Preheat oven to 400°F.
Prepare 1 single-crust pie crust and line a pie plate with it, trimming and folding edges under and crimping into a decorative scallop with your fingers. Set aside while preparing the filling.
1 [unbaked pie crust]
In a large bowl, mix the sour cream, sugar, egg, flour, vanilla and salt until smooth. Gently fold the blueberries into the custard mixture. If you stir the blueberries in too vigorously your whole pie will turn purple! Pour into the unbaked pie crust and then bake in the preheated 400 degree oven for 25 minutes.
1 cup sour cream, 3/4 cup granulated sugar, 1 large egg, 2 Tablespoons all-purpose flour, 2 teaspoons pure vanilla extract, 1/4 teaspoon salt, 2 1/2 cups fresh blueberries
While the pie is baking, prepare the streusel topping. In a medium bowl combine the brown sugar and flour. Mix in the butter with a pastry cutter or just using your hands until crumbly. Mix in the chopped pecans.
1/2 cup light brown sugar, 1/3 cup all-purpose flour, 1/4 cup salted butter, 1/2 cup chopped pecans
When the pie crust and blueberry custard filling has baked for 25 minutes, pull it out of the oven and sprinkle the streusel over the top of the pie. Bake for an additional 15-20 minutes or until filling is set and topping is brown. Watch your crust to make sure it doesn’t burn. Either use a crust shield or make a loose foil tent towards the end of baking to protect the edges of the pie from burning.
Remove from oven and let pie sit for at least 30 minutes. This pie can be served either warm or cold - it's delicious either way!