Apple Crisp

This recipe is from Millie's preschool, believe it or not. It's meant to be so simple a child can do it, and other than peeling and slicing the apples, it really is that easy. It's also the best apple crisp I've ever had, possibly thanks to the entire stick of butter that goes into the crust.

4 medium unpeeled or peeled tart apples, sliced.
3/4 cup of all purpose flour
3/4 cup of packed brown sugar (I used 1/4 and it was plenty sweet)
1/2 cup quick cooking or regular oats (I used quick cooking)
1/3 cup chopped walnuts (a generous 1/3)
1 1/2 tsp ground cinnamon (I used 1/2 tsp)
1/2 cup butter, softened

Heat oven to 375.
Spread apple slices in ungreased 8 inch square pan.
Mix remaining ingredients with fork (I used my hands). Sprinkle over apples.
Bake uncovered until the topping is golden brown and apples are tender and bubbling, about 30 minutes.