Preheat the oven to 375 degrees. Line an 8-inch pie pan with half of the pie dough. Roll out the remaining dough or crust into a round to top the pie. Stir the butter with the flour in a heavy saucepan over low heat to make a smooth paste. Whisk in the cream and sugar. Bring to the boil, reduce the heat, and simmer the filling until it thickens, about 3 minutes, whisking constantly. Add a small portion of the warm liquid to the eggs, then stir them into the pan. Stir in the vanilla. Strain the filling into the lined pie pan. Top with the round of pie dough and crimp the edge decoratively to seal. Cut 4 to 5 slits in the top to allow steam to escape. Bake until the crust is nicely browned and the filling is set, 45 minutes to 1 hour. Serve with the fresh berries or peaches.