Preheat oven to 375 degrees F. Butter the bottom and sides of a 9-inch deep-dish pie plate with the 1 teaspoon butter; set aside.
In a medium bowl combine whipping cream, milk, eggs, flour, granulated sugar, melted butter, vanilla, and salt. Beat with an electric mixer on low speed until smooth. Arrange peaches and raspberries in the prepared pie plate. Pour cream mixture over fruit.
Bake for 50 to 55 minutes or until puffed and lightly browned. Cool on a wire rack for 15 minutes. Sprinkle lightly with powdered sugar (if desired) and garnish with basil. Serve warm.