To prepare the streusel

1. Combine the flour, oats, sugar, and salt in a medium sized bowl and stir to combine. Cut in the butter using a pastry cutter until it comes together in pea-sized clumps. Toss in the sliced almonds. Refrigerate until ready to use.

To prepare the pie

1. Preheat the oven to 400 degrees.
2. Toss the berries, lemon juice, and extracts together in a large bowl. In a separate, smaller bowl, combine the dry ingredients. Add the dry ingredients to the berries bowl and toss to combine. Allow to sit for 20 minutes while you prepare your pie plate.
3. Roll your pie dough to 1/8-1/4″ thick and place in a 9″ standard pie plate. Trim excess dough from the edges and crimp your crust as desired.
4. Spoon the berries into the prepared pie plate and drain off any excess juices. Top the pie evenly with the crumble topping.
5. Whisk together the egg and water to create an egg wash. Brush evenly over all of the pie crust edges.
6. Place pie in the preheated oven and bake at 400 degrees for 30 minutes. Decrease oven temperature to 350 degrees and bake for an addition 1 or 1-1/2 hours, or until the filling bubbles thickly around the outside of the pie.
7. Once done, cool on a cooling rack until room temperature, at least 6 hours or overnight.