Apple Slab Pie, Gluten Free

Instructions

1. 1

   Cut the butter into the flour

   Whisk the gluten-free blend, xanthan gum, granulated sugar, and salt together in a wide bowl, making sure the gum is fully dispersed before any liquid goes in. Scatter in the cold butter and toss to coat, then flatten the cubes into irregular flakes with your fingertips or a pastry blender. Leave them a touch larger than you would with wheat flour — those visible pieces are the only thing creating flakiness here.

2. 2

   Bring the dough together

   Beat the egg with the vinegar, stir it into the ice water, and drizzle the liquid over the flour in stages, tossing with a fork. Gluten-free dough needs more moisture than wheat dough and should feel slightly tackier than you expect — if it looks at all dry or sandy, keep adding water a tablespoon at a time. There's no gluten to overdevelop, so you can work it until it's cohesive. Divide into two flat rectangles, one slightly larger, and wrap tightly.

3. 3

   Rest the dough to hydrate

   Refrigerate for at least 1 hour, and ideally 2. This rest is not optional for gluten-free pastry: the rice flours and starches need time to absorb the liquid, and dough rolled too soon will be gritty and crack along every edge.

4. 4

   Roll and line the pan

   Let the larger rectangle sit out for 10 minutes, then roll it between two sheets of parchment to roughly 18 by 13 inches. Peel off the top sheet, invert the dough over a 15x10x1-inch rimmed baking sheet, and ease it into the corners. Press any cracks or tears back together with your fingers — gluten-free dough patches invisibly, so don't hesitate. Chill the lined pan while you make the filling.

5. 5

   Mix the filling

   Heat the oven to 400°F with a rack in the lower third. Toss the apples with the lemon juice in a very large bowl. Whisk both sugars with the cornstarch, cinnamon, ginger, nutmeg, and salt, then add to the apples along with the vanilla and toss to coat. Assemble right away rather than letting the filling stand.

6. 6

   Fill and top

   Spread the apples evenly over the chilled crust, pressing them flat. Roll the second piece between parchment to about 16 by 11 inches, peel off the top sheet, and invert it over the filling. Trim to a 1/2-inch overhang, fold the rim under, and press it firmly against the pan edge with a fork — gluten-free dough doesn't hold a tall fluted crimp, so a flat fork seal is both sturdier and neater.

7. 7

   Wash, sugar, and vent

   Brush the top thinly with the egg beaten with cream, sprinkle generously with turbinado sugar, and cut about a dozen evenly spaced 1-inch slits. Chill the assembled pie for 20 minutes so the butter is fully firm before baking.

8. 8

   Bake in two stages

   Set the pan on a second baking sheet and bake at 400°F for 20 minutes, then reduce to 375°F and bake another 32 to 38 minutes. Gluten-free crust browns more slowly and less evenly, so judge doneness by the vents: you want thick, syrupy juice bubbling up and a crust that feels firm and dry to a light tap, not just a golden color. Tent loosely with foil if the edges darken before the center is ready.

9. 9

   Cool completely before cutting

   Cool on a wire rack for at least 90 minutes — longer than the wheat version. Gluten-free pastry is fragile while warm and firms up considerably as it cools, so early slicing will crumble the bottom crust. Glaze if you like once the pie is barely warm, then cut 4 by 6 into 24 squares.

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Baker's Tips

• 1.

  Use a mix of apples — firm tart ones like Granny Smith or Northern Spy for structure, plus a softer sweet variety like Golden Delicious or Braeburn that collapses into sauce around them.

• 2.

  Slice the apples a consistent 1/4 inch thick. Thick wedges stay crunchy and leave gaps under the top crust as the thinner pieces shrink.

• 3.

  If the butter starts to look greasy or smeary while you're working the dough, stop and put the whole bowl in the freezer for 10 minutes.

• 4.

  A pan with a true 1-inch rim matters. Anything shallower will overflow with this much filling.

• 5.

  Roll the dough between two sheets of floured parchment if your counter is small or warm — it also makes transferring the big rectangle much easier.

• 6.

  Bake it the day before and leave it uncovered at room temperature overnight; the crust stays crisper than it would under foil in the fridge.

• 7.

  For the cleanest squares, cut with a sharp chef's knife pressed straight down rather than dragged.