GLUTEN FREE PIE
Keeping it gluten-free is a challenge, but it can be done
We wanted a pie that had a firm, juicy filling full of fresh blueberry flavour with still plump berries, and we also wanted a crisp, flaky crust.
To thicken the pie, we tried cornstarch as well as our glutenfree flour blend but preferred tapioca starch, which was subtle enough to allow the berry flavour to shine through. Too much of it, though, created a congealed mess.
Cooking some of the blueberries down to a saucy consistency helped us reduce the amount of tapioca required, as did adding a peeled Granny Smith apple that we shredded on the large holes of a box grater.
Rich in pectin, the apple helped thicken the berries naturally. Since gluten-free pie crusts can easily turn soggy, we found that preheating a sheet pan in the oven and baking the pie on the lower rack helped keep the crust crisp. (We also offer a gluten-free flour blend.)
It’s not safe to place a glass (Pyrex) pie plate on a preheated baking sheet. If you must use a glass pie plate, do not preheat the baking sheet; note, however, that your crust will not be as crisp. This pie is best served the day it is made.
Blueberry Pie
Makes 8 servings
30 ounces (6 cups) blueberries 1 Granny Smith apple, peeled, cored and shredded
5 1⁄4 ounces (3⁄4 cup) sugar 2 tablespoons tapioca starch 2 teaspoons grated lemon zest plus 2 tsp juice
Pinch salt
1 recipe Double-Crust Pie Dough (recipe below)
1 large egg white, lightly beaten
Start to finish: three hours Cook 3 cups of blueberries in a medium saucepan over medium heat, mashing occasionally with a potato masher to help release
the juices, until half of the berries have broken down and the mixture is thickened and measures 1½ cups, about eight minutes. Let cool slightly.
Place shredded apple in a clean kitchen towel and wring dry. Combine apple, cooked berry mixture, remaining 3 cups uncooked berries, sugar, tapioca starch, lemon zest and juice, and salt in a large bowl.
Adjust oven rack to lowest position, place foil-lined rimmed baking sheet on rack, and heat oven to 425 F. Roll one disk of dough into a 12-inch circle between two large sheets of plastic wrap. Remove top plastic, gently invert dough over a 9-inch metal pie plate then ease the dough into the plate; remove remaining plastic. Roll the other disk of dough into a 12-inch circle between two large sheets of plastic. Remove top plastic. Using a 1¼inch round cookie cutter, cut a hole in the centre of the dough, then cut out six more holes, about 1½ inches from the centre hole, evenly spaced around it.
Spread the blueberry mixture evenly into the dough-lined pie plate. Gently invert the top crust over the filling and remove remaining plastic. Trim dough ½ inch beyond the lip of the pie plate, pinch dough edges together, and tuck it under to be flush
with the pie plate edge. Crimp dough evenly around the edge using your fingers. Brush the pie with egg white.
Place the pie on a preheated baking sheet and bake until crust is light golden brown, about 25 minutes. Reduce oven temperature to 350 F, rotate the sheet and continue to bake until juices are bubbling and the crust is deep golden brown, 30 to 40 minutes longer. Let pie cool on a wire rack to room temperature, about four hours. Serve.
Double Crust Pie Dough
Makes enough for one 9-inch pie Perfect pie dough has just the right balance of tenderness and structure. The former comes from fat, the latter from the long protein chains, called gluten, that form when flour mixes with water. Too little gluten and the dough won’t stick together; too much and the crust turns tough.
So presumably we would face mostly a structural issue with a gluten-free dough, since glutenfree flours are naturally low in protein. As our first step, we swapped in our gluten-free flour blend for the wheat flour in all the pie dough recipes the test kitchen has developed over the years. We produced workable doughs in every case, but an all-butter dough (with sour cream for tenderness) had the necessary richness to stand up to the starchiness of the gluten-free flour blend and was the best starting point.
Although we weren’t surprised to find that the dough was still too soft and lacked structure, we were taken aback by how tough it was; on its own, the sour cream was not sufficient to tenderize a gluten-free dough. We solved the structural problem easily with the addition of a modest amount of xanthan gum, but flakiness and tenderness were still elusive.
In an effort to further tenderize our dough, we tested ingredients that are known to tenderize: baking soda, lemon juice, and vinegar. Vinegar was the clear winner, producing a pie crust that was not only tender, but also light and flaky. Like conventional recipes, this pie dough can be prepared in advance and refrigerated for two days; however, it is not sturdy enough to withstand freezing.
6 tablespoons ice water
3 tbsp sour cream
1 tbsp rice vinegar
13 ounces (2 cups plus 2 tbsp) ATK Gluten-Free Flour Blend (recipe below)
1 tbsp sugar
1 teaspoon salt 1⁄2 tsp xanthan gum
16 tbsp unsalted butter, cut into 1⁄4-inch pieces and frozen for 10 to 15 minutes
Combine ice water, sour cream, and vinegar in a bowl. Process flour blend, sugar, salt and xanthan gum together in a food processor until combined, about five seconds. Scatter butter over top and pulse until crumbs look uniform and distinct pieces of butter are no longer visible, 20 to 30 pulses.
Pour half of the sour cream mixture over the flour mixture and pulse to incorporate, about three pulses. Add remaining sour cream mixture and pulse until dough comes together in large pieces around blade, about 20 pulses.
Divide dough into two even pieces. Turn each piece onto a sheet of plastic wrap and flatten it into a 5-inch disk. Wrap each piece tightly in plastic and refrigerate for one hour. Before rolling out dough, let it sit on counter to soften slightly, about 30 minutes. (Dough can be wrapped tightly in plastic and refrigerated for up to two days.)
Gluten Free Flour Blend
Makes 42 ounces (about 9 1/3 cups)
It is important to bring the mix to room temperature before using it in a recipe. Be sure to use potato starch, not potato flour. Tapioca starch is also sold as tapioca flour; they are interchangeable.
24 ounces (4 1⁄2 cups plus 1⁄3 cup) white rice flour
7 1⁄2 ounces (1 2⁄3 cups) brown rice flour
7 ounces (1 1⁄3 cups) potato starch
3 ounces (3⁄4 cup) tapioca starch
3⁄4 ounce (3 tablespoons) nonfat milk powder
Whisk all ingredients together in large bowl until well combined. Transfer to airtight container and refrigerate for up to three months.
Per serving: 506 calories (227 calories, or 45 per cent from fat; 26 grams fat (15 g saturated; 1 g trans fats); 63 milligrams cholesterol; 339 mg sodium; 70 g carbohydrate; 7 g fibre; 34 g sugar; 6 g protein.