To make the crust: Sift together the flour, sugar and salt.
Add 1 cup cubed butter or butter flavored vegetable shortening.
Use a pasty cutter or a food processor to cut the butter into the dry ingredients until it resembles coarse corn meal.
Add 6-8 Tbsp of ice water 2 Tbsp at a time until it forms a soft dough.
Turn out onto a silpat or lightly floured surface, and turn just until it comes together. Form into a flattened disc and wrap in plastic wrap. Rest in the fridge for at least 1 hour or overnight.
To assemble: Unwrap chilled dough place onto a silicone mat or lightly floured surface. Use a floured rolling pin and roll into approximately a 17 x 14-inch rectangle leaving enough overhang to form the sides of the crust.
Lightly spritz a Spray a 15x10x1-inch jelly roll pan with baking spray or butter. Fit crust into pan forming an edge. Keep chilled while you prepare the apples and streusel.
For the apples: Toss sliced apples with all-purpose flour, granulated sugar, brown sugar, apple pie spice and ground cinnamon. Arrange the apples over the crust.
For the streusel: In a small bowl, toss together the vanilla wafer crumbs with 1/2 cup brown sugar.
Using a food processor or pastry cutter, cut 1/2 cup cold butter into the crumbs until it resembles peas.
Sprinkle the walnuts over the apples first, then top with the buttered vanilla wafer crumbs. Sprinkle 1/4 cup toffee bits on top.
Place into a preheated 375°F oven. Bake for 45-50 minutes until the streusel is golden and the apples are tender. Serve warm or at room temperature.