Stir together all the ingredients except the butter in a large bowl.

Sprinkle in the butter pieces and toss to coat.

Rub the butter into the dry ingredients with your fingertips until the butter is incorporated and the mixture is chunky but not homogenous.

Press evenly into the bottom and up the sides of an ungreased, preferably metal 9-inch pie pan.

Freeze until solid, about 15-20 minutes.

Bake in the middle oven rack for 18-20 minutes.

(I’ve made this crust a few times and it tends to “slump” while baked – I simply reform the crust back into place using a small spatula before filling and baking further.)

While the oat cookie crust is baking, place a medium sized pot on the stovetop. Place the blueberries, lemon juice, sugar and cornstarch in the pot; mix together to coat the berries.

Set the heat to medium and cook the berry mixture until bubbly and thickened, stirring occasionally – about 15 minutes. (make the streusel while the blueberries are on the stovetop and the crust is in the oven!)

Stir together the flour, sugars and salt in a large bowl.

Sprinkle in the butter pieces and toss to coat.

Rub the butter into the dry ingredients with your fingertips until the butter is incorporated and the mixture is chunky but not homogenous.

Chill for 15 minutes in the freezer.

Pour the blueberry mixture into the oat cookie crust.

Sprinkle the streusel topping over top of the blueberry mixture, covering the pie.

With the oven still on at 350 degrees, bake the pie for 35-40 minutes, set on a baking pan lined with parchment paper until the streusel looks nice and browned and the filling is bubbling and thickened.

Let pie sit for 3-4 hours to cool down and thicken.

Serve with the best vanilla ice cream you can find!