Preheat oven to 375 degrees. On a lightly floured surface, roll out pie crust into a 12-inch circle, about 1/8" thick. Fit crust into a 9-inch pie plate. Fold edges under and crimp. Using a fork, prick the bottom and sides of crust.
Line with parchment paper and fill with pie weights. Bake for 20 minutes. Remove weights and parchment, and transfer to a baking rack and cool for 30 minutes.
Peel 5 of the peaches. Slice into 1/4 inch slices. Arrange the peach slices in overlapping concentric circles in the pie crust.
In a medium mixing bowl, whisk together sour cream, egg yolks, sugar, flour and vanilla just until blended. Pour custard over peach slices in pie plate.
Bake pie 30 minutes or just until the custard begins to set. If the crust is browning too quickly, cover the edge loosely with aluminum foil.
Meanwhile, make streusel topping by combining butter, flour, sugar, and cinnamon with your until the mixture resembles coarse crumbs.
After the initial 30 minute baking, remove the pie from the oven and evenly sprinkle the top with the streusel topping. Return the pie to the oven and bake another 15 minutes longer or until the streusel is nicely golden and a knife tip inserted into the center comes out of the pie clean.
Cool pie completely on a wire rack before serving. Top decoratively with remaining peach and serve.