Crust:

1 stick (1/2 cup or 115g)unsalted butter

3/4 cup (115 g) flour

1.5 tsp sugar

1/2 tsp fine salt

1/4 cup ice cold water

Filling:

3 lbs apples, (2lbs granny smith or other tart, firm apple, and 1lb sweet medium firm like fuji)

1/4 cup flour

1 tbs cinnamon

1/3 cup brown sugar

2/3 cup white sugar

3 tbs cold unsalted butter cut in 1/4 dice

Pinch of salt

Topping:

1/2 cup Unsalted butter

1 cup Flour

2/3 cup Brown sugar

1 tbs granulated sugar

Egg wash:

1 beaten egg

1 tbs water or milk

Make the crust. Cube the butter into 1/4 inch cubes and chill. Combine flour, salt, and sugar in a medium bowl. Toss butter cubes to coat. Smash each butter cube between your thumb and index finger to flatten. When all butter cubes have been flattened, stir in ice cold water and mix until dough pulls away from the side of the bowl. On a floured surface roll out dough into a 1/4 inch thick rectangle. Fold into thirds, then wrap in plastic and chill for 30 minutes. (Can be made in advance and refrigerated for 1 day or frozen for 1 month)

Make filling.

Peel and core the apples, and slice into 1/4 inch thick slices. Place apple slices in a large bowl. In a small bowl, combine flour, sugars, cinnamon, and salt. Toss the apples with the flour mixture, cover loosely with plastic or a tea towel and set aside to macerate for 20-30 minutes. (Can be made up to 1 day in advance. If making in advance, toss apple slices with 1 tbs lemon juice, and add an extra tsp of flour to the flour mixture. Keep refrigerated until ready to use).

Make topping. Cube butter. In a medium bowl combine flour and sugars. Toss butter wth flour mixture and rub together until the mixture is the texture of sand. (Can be made 1-3 days in advance and kept refrigerated)

Assemble and bake:

Preheat oven to 425 degrees F. Line glass pie plate with pie crust and crimp edge. Layer apple mixture in crust, sprinkling with finely cubed butter bits as you go. Pour in any juices that have collected at the bottom of the apple bowl. Brush a bit of egg wash on the exposed edges of the pie crust. Top the pie with the streusel topping. Bake until bubbling and apples are soft, but not dissolved, about 35-45 minutes. Cover the crust edged with a strip of foil if they begin to brown too quickly.

Cool for at least 2 hours before serving. All components can be made a day in advance. Assemble the pie just before baking.