1/2 pie dough or 1 prepared pie crust
Prepare pie dough: Roll out pie dough to about 1/8-inch thick and fit into a regular pie plate. Trim edge to 1/2 inch; fold under and crimp. Pierce bottom of dough all over with a fork. Transfer to freezer for 30 minutes. Preheat oven to 400 right before you take it out.
Make streusel: Stir confectioners’ sugar, baking powder, salt and three tablespoons flour together in a small bowl. Add bits of cold butter, and either using a fork, pastry blender or your fingertips, work them into the flour mixture until it resembles coarse crumbs. Add flour as needed.
Par-bake crust: Tightly press a piece of aluminum foil against frozen pie crust. From here, you ought to fill the shell with pie weights. Bake for 10 minutes, then carefully remove foil and any weights, press any bubbled spots in with the back of a spoon, and return the crust to the oven for another 5 to 8 minutes, or until it is lightly golden brown. Transfer to a wire rack to cool slightly. Reduce oven temperature to 375. *Skip this step if you don’t mind a slightly soggy bottom.
Make the filling: Sprinkle quartered peaches with sugar and salt and let sit for 10 minutes. Spread two tablespoons creme fraiche in bottom of par-baked pie shell, sprinkle with 1/3 of the streusel and fan the peach quarters decoratively on top. Dot the remaining three tablespoons of creme fraiche on the peaches and sprinkle with remaining streusel.
Bake the pie: Until the creme fraiche is bubbling and the streusel is golden brown, about 50 minutes. Cover edge of crust with a strip of foil if it browns too quickly. Let cool on a wire rack at least 15 minutes before serving.