Strawberry-Rhubarb Slab Pie

To prepare crust: Place a foil-lined baking sheet on bottom rack of oven to collect any drips from the pie. Preheat oven to 400 degrees F. Mix all-purpose flour, whole-wheat flour and salt in a large bowl or food processor. Cut in butter using a pastry blender or 2 knives, or by pulsing in the food processor, until the butter forms pebble-size pieces with the flour. Add ice water, 2 tablespoons at a time, until the dough is evenly moistened (but not wet) and is just starting to clump together. Be careful not to overwork the dough. Divide the dough into 2 pieces, one slightly larger than the other. Pat each piece of dough into a 1 1/2-inch-thick disc. Wrap the smaller disk of dough in plastic wrap and refrigerate while you do the next 2 steps, or about 30 minutes.

Meanwhile, roll the larger piece of dough between 2 sheets of parchment or wax paper into a 12-by-16-inch rectangle. Peel off the top sheet of paper and invert the dough onto a 10-by-14-inch jelly roll pan; press lightly to fit it into the pan. Trim any crust hanging over the edge. This is the bottom crust. Cover and refrigerate while you make the filling.

To prepare filling and bake pie: Combine strawberries, rhubarb, 1/2 cup granulated sugar, brown sugar, tapioca, orange zest and juice, cinnamon, vanilla and salt in a large bowl; toss to coat.

Roll out the smaller piece of dough between 2 sheets of parchment or wax paper to a thickness of slightly less than 1/4 inch. This is for the top crust. Peel off the remaining paper from the bottom crust. Using a pastry brush, moisten the outer edges of the crust with water.

Scrape the filling onto the bottom crust, spreading evenly. Using a cookie cutter, cut out shapes from the top crust. Arrange the shapes, slightly overlapping, over the filling. Brush the crust with egg mixture and sprinkle with the remaining 1 tablespoon sugar.

Place the pie on the middle oven rack, then reduce temperature to 375 degrees F. Bake until the crust is deep golden brown and juices are bubbling in the center, 55 to 65 minutes. Let cool on a wire rack. Serve warm or at room temperature.