This Peach Blueberry Almond Crust Galette is a seasonal treat, a perfect summer dessert.
As I walked through the farmer’s market this week amid stalls piled high with fruits, vegetables and flowers, the ripe, blushing rosy peaches and blue-as-midnight blueberries spoke to me. I scrutinized the offerings of rival fruit vendors several times assessing what else was available but ultimately could not resist the tempting appearance and fragrance of the peaches and blueberries. I was inspired to put both to use immediately in a fruit dessert, a rustic Peach Blueberry Almond Crust Galette.
My challenge was to bake a galette with glistening fruit and luscious taste but with a handcrafted look, similar to those produced by professional bakers. Having baked many fruit pies, tarts and galettes over the years, I knew that a proper thickener is critical to a galette’s success in addition to the freshest peaches and blueberries. A galette with a watery filling results from insufficient thickener; one with a pasty or rubbery filling results from too much thickener. Both are undesirable. Since peaches are generally juicier than blueberries, I had to figure out how to thicken this fruit combination so that the ripe flavors and gorgeous colors were displayed at their peak without excessive juiciness or starchiness or dullness. So some research was in order to update my knowledge of available thickeners to understand how they work and what result can be expected from each.
Although flour and cornstarch are commonly used as thickeners, both have certain qualities that, in my view, make them less desirable for baked fruit-filled desserts. Cornstarch creates a shiny, smooth but cloudy, semi-transparent filling which thickens at the boiling point, 212° F (100°C). Unfortunately, to assure full thickening power, the filling has to bubble for several minutes which may overcook peaches and blueberries. Failure to cook long enough, however, results in a filling with a chalky or floury taste. But cooking too long at 212° F (100°C) weakens cornstarch’s thickening efficacy. Cornstarch also becomes weepy, exuding liquid when refrigerated or frozen.
Flour, on the other hand, is one of the mildest, slowest and most stable thickeners for baked fruit desserts. Since twice as much flour is needed to get the same thickening capacity as cornstarch, flour thickens fruit nicely but leaves more of a matte, slightly opaque filling often with a pasty taste if not cooked long enough. Here again, while flour starts to thicken at 144°F to 162°F (62°C to 72.5°C) and completes the final thickening process at 205°F (96°C), the filling needs to be baked thoroughly for least 10 minutes at 205°F (96°C) to achieve maximum thickening but may result in mushy fruit.
My usual go-to thickener for single fruit tarts and pies is tapioca. Tapioca,* with twice the thickening ability of all-purpose flour, is a good choice for pie fillings because it produces a bright, clear, glossy filling without a starchy flavor. Tapioca thickens at a lower temperature than cornstarch. While there is less chance of overcooking fruit, tapioca becomes less effective the longer it is cooked. Tapioca pearls or too large beads may give the filling a stippled and gluey texture. Tapioca remains stable when refrigerated or frozen.
Although quick research confirmed that tapioca is probably the most suitable of the conventional thickeners available to home bakers to produce the galette I envisioned, I discovered internet references to commercial baking of fruit pies, and learned that professional bakers do not use cornstarch, flour nor tapioca in fruit fillings, but instead rely on a modified maize starch called Clearjel®.**
First a little history: Clearjel® was introduced in 1948 by National Starch Company (now Ingredion Incorporated) for the commercial food industry to withstand the heat necessary to process products such as canned pie filling, and has been used successfully for almost 70 years.
Fascinated with the chemistry of baking, I was intrigued to discover this new (to me) thickener. In trying to source a test amount, I learned that, although the US Department of Agriculture approves Clearjel for commercial baking and home canning of fruit pie fillings, and tons of it have been used commercially over the years, it has not been marketed to home bakers and is available primarily online, not in traditional grocery stores. So I bought regular Clearjel online*** and experimented with my peach and blueberry combination to see how this white cornstarch-looking powder would work.
Without belaboring the technical aspects of why and how Clearjel works, here is what I learned in a nutshell: Clearjel is made from waxy maize (a high protein Chinese corn valued by body builders) which gives the fruit filling greater textural stability than ordinary corn starch (which can become runny) and contains nearly 100% of amylopectin, one of two essential components of starch which determine a starch’s thickening characteristics. Waxy maize combined with cross linking of chemical bonds between the starch polymers allows starch granules to swell, not disintegrate in high heat processing like canning or baking. For a layman’s description of waxy maize and how it works, see https://en.wikipedia.org/wiki/Waxy_corn .
In using regular (also referred to as cook-type) Clearjel, I discovered why it is used widely by professional bakers. A cooked Clearjel filling is clear and smooth without a floury, pasty or starchy aftertaste. Clearjel is easy to use. It absorbs some of the juices exuded by the fruit before baking, but starts to thicken as the filling is heated at lower temperatures than other starches, avoiding the risk of overcooking fruit. Clearjel differs from conventional thickeners in that the filling is only partially thickened during cooking with maximum thickening occurring as it cools over 24 hours. A Clearjel thickened filling is stable and resists weeping during refrigeration or freezing.
The amount of Clearjel needed depends on the juiciness and the fruit’s natural pectin in the filling.**** Peaches are juicy, but with moderate amounts of pectin; blueberries, on the other hand, are less juicy but rich in pectin. In this Peach Blueberry Almond Crust Galette I found I needed slightly more than ¾ as much Clearjel as tapioca which produced a galette with soft, yet distinct, fruit, with set, but not jellied juices, with a luminous appearance and a crisp almond crust. Just what I wanted.
For those not interested in experimenting with Clearjel, this Peach Blueberry Almond Crust Galette can be made with a tapioca thickener with great results, but be sure to let the tapioca soften in fruit juices for at least 5 minutes before baking to permit the tapioca to swell maximizing thickening ability. I provide the quantity of tapioca needed for a soft yet set filling. While I made this recipe as a galette because I wanted a more casually appearing dessert, it certainly can be made into a 9 inch (23 cm) pie or tart.
Peach Blueberry Almond Crust Galette
Ingredients for crust
6¾ ounces (191.3g) unbleached all-purpose flour, more for rolling
½ cup (48g) almond flour
1 tablespoon granulated sugar
½ teaspoon salt
5½ ounces (156g) unsalted butter, chilled and cut into ½ inch dice
1 large egg yolk
¾ teaspoon almond extract
2 ½ tablespoons milk
Ingredients for filling
3-4 large peaches, peeled and cut into ½ inch slices (about 3 cups)
2 cups blueberries, rinsed and dried
¼ cup dark brown sugar, firmly packed
2 tablespoons granulated sugar
3 tablespoons regular NOT Instant Clearjel** or 4 tablespoons instant tapioca, ground finely
¼ teaspoon ground cinnamon
Zest of half lemon
Pinch of table salt
1 large egg, beaten
2 tablespoon sanding or demerara sugar
½ cup or more flaked almonds
Preparing crust: Combine all-purpose and almond flours, sugar and salt in a stand mixer fitted with a paddle attachment. Add the butter to the flour. Mix at low speed until flour looks like coarse sand and holds together when squeezed in your hand, 1 to 2 minutes. Break up lumps of butter larger than the size of peas. Some butter chunks should remain.
In a small bowl, beat egg yolk and milk and combine with flour mixture. Mixing on low speed just until dough comes together, about 15 seconds; dough will be somewhat soft. Turn dough out onto a sheet of plastic wrap, shape it into a flat disk with smooth edges, wrap it in plastic, and refrigerate for at least 30 minutes or overnight before rolling out. If dough has been refrigerated longer than 30 minutes, allow it to warm at room temperature for 10 to 15 minutes, until it rolls easily. Use pastry within a few days or freeze.
When ready to bake, position a rack in the center of the oven and preheat the oven to 350°F (180 °C). Line a large rimmed baking sheet with parchment paper or a silicone baking mat.
Preparing filling:
Peeling peaches: Make an ice bath by placing 4 cups of ice and 4 cups of water in a bowl and set aside. Bring a medium saucepan of water to a rolling boil.
With a slotted spoon, lower each peach into the boiling water. Leave it there for no more than 30 seconds. Remove immediately and plunge it into the ice water bath. After 10 seconds or so, grab the peach and pinch a piece of skin near the stem end to get started; then simply peel. The skin will slip off easily. If it doesn’t, then peach is too hard and a knife should be used for peeling.
Continue peeling remaining peaches.
If thickening with tapioca, grind tapioca granules to a fine powder in a food processor or blender. If thickening with Clearjel, in a small bowl, mix the two sugars, Clearjel, cinnamon, lemon zest and salt.
Slice each peach into 8 wedges over a medium bowl to catch juices. Add blueberries and the Clearjel-sugar-spice mixture and stir so that each piece of fruit is coated. Cover bowl and let stand for 30 minutes so juices released can start to be absorbed by the thickener. Proceed to prepare crust.
Lightly flour a large work surface and roll out the dough to a 12- to 13-inch round. Trim the edge of the circle if desired.
Transfer dough to prepared baking sheet. Arrange the fruit in the center of the dough, leaving an edge of about 2-3 inches (5-7.5 cm) of space around the perimeter. (I arranged the peaches 3 inches from edge of dough and the blueberries in the center with a few peaches on top, but any arrangement will work.) Fold the outside edge of the dough over the fruit, making occasional pleats. Press each fold to seal. Pour any fruits juices, sugar and thickener left over in the bowl over the filling.
Brush crust with beaten egg. Scatter and press flaked almond along the dough edge to assure adherence. Sprinkle coarse sugar evenly over dough and fruit.
Bake the galette for 20 minutes, then check. If crust and almonds are browning too fast, cover galette with aluminum foil. Continue baking for another 30 minutes until the crust turns a light brown and the filling bubbles.
This galette can be served warm or room temperature directly from the baking sheet, but the galette should be cooled completely so it firms up before moving it to a serving plate. Cut into wedges and served plain or with a scoop of vanilla ice cream, lightly sweetened whipped cream or a dollop of crème fraiche.
Serves: 8-10
This galette tastes best the day it is baked, but it will still taste great for up to 3 days, if refrigerated, covered with plastic wrap.
*Tapioca, made from the cassava root, is commonly available in three forms: pearls, quick-cooking beads, flour and starch. Tapioca flour and starch are ready to use as a thickener. Pearl or quick-cooking tapioca should be ground in a food processor or blender to a powder for smooth, lump-free thickening.
**Two types of Clearjel are available, “regular” and “instant.” “Regular” must be heated to thicken and is preferred for use in baked goods. “Instant” does not require heat to thicken; it thickens once liquid is added. Other similar products, also approved by USAD, are available online under the brand names PermaFlo®, ThermFlo® and ThickGel®.
*** Regular, not Instant, Clear Jel® can be sourced at https://www.myspicer.com/shop/clear-gel/; https://www.amazon.ca/National-Starch-ClearJel/dp/B000FRUOA4; https://rockrunonline.com/product/clear-gel-regular/; https://www.kitchenkrafts.com/product/clearjel-starch/top-rated-products.
**** There are numerous tables online which provide proportions of Clearjel needed to substitute conventional thickeners. The most helpful information can be found at http://www.kingarthurflour.com/guides/pie-baking/pie-thickener.html
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