Preheat your oven to 400°F and fit the 9-inch unbaked pie crust into a 9-inch deep-dish pie plate, crimping the top edges firmly.

Line the crust with parchment paper, fill to the top rim with pie weights, and bake at 400°F for 12 minutes.

Remove the parchment paper and pie weights, then return the crust to the oven for 3 minutes until the bottom appears dry and pale gold.

Remove the par-baked crust from the oven, reduce the oven temperature to 375°F, and let the crust cool on a wire rack.

In a large mixing bowl, combine 1.75 lbs sliced Granny Smith apples, 1.75 lbs sliced Honeycrisp apples, 0.5 cup granulated sugar, 0.25 cup packed dark brown sugar, 1 tbsp lemon juice, 1.5 tsp ground cinnamon, 0.25 tsp ground nutmeg, and 0.25 tsp salt.

Set the apple mixture aside at room temperature for 30 minutes to release excess fruit juices.

Drain the liquid from the apples into a small saucepan, keeping the apple slices in the bowl.

Simmer the drained juices in the saucepan over medium heat for 5 minutes until reduced to 3 tablespoons of syrup, then pour the syrup back over the apples.

Sprinkle 3 tbsp cornstarch over the apples and toss thoroughly until no dry white starch remains visible.

In a separate medium bowl, mix 1 cup all-purpose flour, 0.5 cup rolled oats, 0.5 cup packed dark brown sugar, 0.25 cup granulated sugar, 0.5 tsp ground cinnamon, and 0.25 tsp salt.

Add 0.5 cup cold cubed unsalted butter to the dry topping ingredients and work it with a pastry cutter until irregular crumb clusters form.

Arrange the apple slices in the par-baked crust, pressing them down firmly to avoid gaps.

Spread the streusel topping evenly over the apples, pressing lightly so the crumbs cling together.

Bake at 375°F for 55 minutes until the streusel is deep golden brown and thick juices bubble around the edges.

Set the pie on a wire rack to cool for 180 minutes before cutting into slices.