Open-Face Apple Maple Pies with Walnut Crumble

Steps

1. Make the crust: whisk the whole wheat flour, all-purpose flour, salt and granulated sugar in a large bowl.
2. Cut three-quarters of the cold butter into the whole wheat and all-purpose flour mixture until pea-size pieces remain; keep the remaining quarter of the butter cold for the crumble.
3. Drizzle in the ice-cold water a little at a time, tossing until the dough just holds together. Divide into two disks, wrap and chill 1 hour.
4. Make the crumble while the dough chills: mix the oats, walnuts, half of the brown sugar and half of the cinnamon, then rub in the remaining quarter of the cold butter until clumpy. Refrigerate.
5. Make the filling: toss the apple with the lemon juice, maple syrup, the remaining half of the brown sugar, the remaining half of the cinnamon, the nutmeg and the cornstarch. Let stand 15 minutes.
6. Preheat the oven to 400°F (200°C) with a rack in the lower third.
7. Roll each dough disk into a 12-inch round and fit into two 9-inch pie plates; crimp the edges and chill 15 minutes.
8. Divide the apple filling and its juices evenly between the crusts, mounding slightly in the center.
9. Scatter the crumble evenly over both pies, leaving the tops open with no top crust.
10. Bake 20 minutes, then lower the oven to 350°F (175°C) and bake 40 to 45 minutes more, until the crust is deep golden, the crumble is crisp and the juices bubble thickly at the center; tent with foil if the crumble browns too fast.
11. Cool the pies on a rack at least 2 hours so the filling sets, then cut each pie into 6 slices.