Mixed Berry Crumb Bars, Gluten Free

Instructions

1. 1

   Heat the oven and line the pan

   Set a rack in the center of the oven and heat it to 375°F. Line a 9x13-inch pan with parchment, leaving a few inches hanging over the two long sides so you can lift the whole slab out later. A metal pan gives you crisper edges than glass; if glass is what you have, expect to add about five minutes at the end.

2. 2

   Mix the dry ingredients

   In a large bowl, whisk the gluten-free flour blend, xanthan gum, granulated sugar, brown sugar, baking powder, salt, and cinnamon until completely uniform. Gluten-free blends settle and clump in the bag, so whisk longer than feels necessary — 30 seconds of real mixing. If your blend already lists xanthan gum or guar gum on the label, leave it out here.

3. 3

   Cut in the butter

   Scatter the cold butter cubes over the dry ingredients. Work them in with a pastry cutter, two forks, or your fingertips until the mixture looks like coarse sand with plenty of butter pieces still visible at pea size and smaller. Keep the butter cold and distinct — those pockets are what make the base short and the topping craggy instead of dense.

4. 4

   Add the egg and vanilla

   Beat the egg with the vanilla in a small bowl, pour it over the crumbs, and toss with a fork until the dough is evenly moistened and clumps when squeezed. It will feel noticeably drier and sandier than a wheat dough at this stage — that's expected, don't add liquid.

5. 5

   Rest the dough

   Cover the bowl and let the dough sit at room temperature for 25 minutes. Rice flour and starches absorb moisture slowly, and this rest is what turns a gritty crumb into a tender one. The dough will look damper and hold together more willingly afterward.

6. 6

   Press and blind bake the crust

   Measure out about 2 1/2 cups of the rested dough and refrigerate it for the topping. Tip the rest into the pan and press it into a firm, even layer, using the flat bottom of a measuring cup to compact it into the corners. Press harder than you would with wheat dough — gluten-free crusts need the extra compaction to hold their shape. Bake for 15 to 17 minutes, until the surface looks dry and matte and the edges are lightly golden.

7. 7

   Toss the berry filling

   While the crust bakes, stir the berries together with the granulated sugar, cornstarch, lemon juice, zest, and salt until no white streaks of cornstarch remain. Do this just before you need it so the fruit doesn't sit and weep. If you're using frozen berries, keep them frozen and toss them straight from the bag.

8. 8

   Assemble

   Spoon the berries over the hot crust in an even layer, leaving behind any loose liquid pooled at the bottom of the bowl. Squeeze the chilled dough into irregular clumps and scatter them over the fruit, leaving gaps for steam to escape.

9. 9

   Bake until the fruit bubbles

   Return the pan to the oven for 42 to 48 minutes. Gluten-free topping takes on color faster than it sets, so judge by the filling rather than the crumbs: you want thick, slow bubbles coming up through the gaps across the whole pan, not just at the edges. If the top is browning hard before the center bubbles, tent it loosely with foil and keep going.

10. 10

    Cool completely before slicing

    Set the pan on a wire rack and leave it for at least 4 hours — gluten-free bars firm up more slowly and need the extra time. For clean edges, chill the cooled pan for an hour, lift out the slab by the parchment, and cut with a long knife, wiping the blade between cuts. Dust with powdered sugar just before serving.

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Baker's Tips

• 1.

  Cold butter is the whole trick. If your kitchen is warm and the dough starts looking greasy or pasty, chill the bowl for 15 minutes and carry on.

• 2.

  Frozen berries work beautifully and don't need thawing — add 5 to 8 minutes to the final bake and expect a slightly looser filling.

• 3.

  If you're using only very juicy fruit like strawberries or sliced peaches, add an extra tablespoon of cornstarch to keep the filling sliceable.

• 4.

  Short on time? Swap the fresh fruit for 2 cups of thick jam or preserves spread over the crust. Skip the sugar, cornstarch, and lemon entirely.

• 5.

  Pressing the base firmly matters more than people expect. A loosely pressed crust crumbles apart when you lift the bars out.

• 6.

  A handful of sliced almonds or rolled oats tossed into the reserved topping adds crunch without changing anything else about the recipe.