Mom's Apple Squares

Whisk whole-wheat flour, all-purpose flour, 2 tablespoons sugar, salt and baking powder in a large bowl. Cut butter into small pieces and quickly rub them into the dry ingredients with your fingers until smaller but still visible. Add oil and toss with a fork to combine. Whisk water and egg yolk in a small bowl. Add to the flour mixture and stir until it begins to come together. Knead the dough with your hands in the bowl a few times until it forms a ball. Divide the dough in half and shape into 5-inch disks. Wrap each in plastic and refrigerate for at least 1 hour.

Preheat oven to 400 degrees F. Coat a 9-by-13-inch baking pan with cooking spray and line the bottom and sides with parchment paper.

Combine apples, the remaining 3/4 cup sugar and cinnamon in a large bowl.

Roll one portion of dough between sheets of parchment or wax paper into a 9-by-13-inch rectangle. Peel off the top sheet and invert the dough into the prepared pan. Peel off the remaining paper. Trim the dough so it covers just the bottom of the pan. Spread the apple filling evenly over the dough. Using the parchment or wax paper, roll out the remaining dough, invert it over the filling and trim the edges so it just covers the filling. Whisk the egg white in a bowl until frothy and evenly brush over the top crust. Lightly sprinkle the crust with additional sugar, if desired.

Bake until golden brown and bubbling, 40 to 45 minutes. Let cool for at least 1 hour before cutting into 12 squares.