Place a foil collar or pie shield around the edges of your fully blind-baked 9-inch pie crust. Set aside. Preheat oven to 425°F.
For the apple pie filling: In a large skillet over medium heat, add the 3 tablespoons of butter, ½ cup brown sugar, ½ cup granulated sugar, cinnamon, ginger, nutmeg, and salt. Cook until the butter is melted and everything is combined.
Stir in the apples and 1 teaspoon of vanilla extract until well coated. Cook, stirring occasionally, until the apples are tender.
Carefully ladle out ¼ cup of hot liquid from the skillet into a small bowl. Whisk in the 3 tablespoons of cornstarch until smooth to create a slurry. Pour the slurry back into the skillet with the apples and cook for about 5 minutes, stirring continuously, until the filling thickens (if not thick enough, stir in an additional mini slurry of 1 teaspoon cornstarch + 1 tablespoon liquid). Remove from heat.
Carefully pour the warm apple filling into your prepared pie crust.
For the streusel: In a medium bowl, combine the flour, ⅓ cup brown sugar, ⅓ cup granulated sugar, melted butter, cinnamon, and vanilla extract. Stir together until a crumbly.
Sprinkle the streusel topping evenly over the apple filling, taking it all the way to the edges. Bake at 425°F for 15 to 20 minutes, or until the streusel topping is set, fully cooked, and golden brown.
Transfer to a wire rack and cool before slicing and serving. Enjoy!