Apple Slab Pie recipe.

Ingredients
1 1/2 cups all-purpose flour
1 1/2 tablespoons white sugar
1/2 cup shortening
1/4 teaspoon salt
1/2 teaspoon baking powder
2 egg yolks, beaten
4 tablespoons water
8 apples - peeled, cored and cut into thin wedges
2 tablespoons lemon juice
2 tablespoons all-purpose flour
1 3/4 cups white sugar
1/2 teaspoon ground cinnamon
2 tablespoons butter
1 cup all-purpose flour
1 teaspoon ground cinnamon
2/3 cup brown sugar
2/3 cup butter

Directions
Preheat oven to 350 degrees F (175 degrees C.) In a large bowl, combine flour sugar, salt and baking powder. Cut in shortening until mixture resembles coarse crumbs. Mix egg yolk and water together and mix into flour until it forms a ball. Roll out to fit the bottom of a 10x15 inch pan.
In a large bowl, combine apples, lemon juice, 2 tablespoons flour, sugar and cinnamon. Pour filling into pie crust and dot with 2 tablespoons butter.
In a medium bowl, combine 1 cup flour, 1 teaspoon cinnamon, 2/3 cup brown sugar and 2/3 cup butter. Cut in the butter until crumbly, then sprinkle over apples.
Bake in the preheated oven for 60 minutes, or until topping is golden brown.