Combine crust ingredients. Work in butter until it is just pea-sized, and use only as much water as needed to make the dough cohesive. Wrap well in plastic wrap and refrigerate for a few hours or a few days.
Roll out dough to equal thickness and place in pie dish. Cover with plastic wrap and freeze while preparing the filling, or freeze for several days.
Preheat oven at 375-degrees. Peel and core apples and slice to 1/8s or smaller. Toss them in a light dusting of flour to prevent sticking. Place apples in pie crust on a cookie sheet.
In a small bowl, whisk together the vanilla extract, lemon juice, flour, and maple sugar; it'll form a thick maple paste. Set aside.
In another small bowl, combine the topping ingredients. Use a fork and knife to reduce the butter to pea-sized chunks.
Return to the maple sauce. Give it a good stir, and drizzle thick syrup all over apples. Cover evenly with crumb topping.
Bake for 40-45 minutes, or until the apples are tender when stabbed with a fork.
OM NOM NOM!