Preheat the oven to 350°F.
In a saucepan, combine the water, 3/4 cup brown sugar, cornstarch, salt, 1 teaspoon of cinnamon, 1/2 teaspoon of grated nutmeg, and pepper, whisk until smooth. Place the pan over high heat and bring to a boil. Reduce the heat to medium and simmer for 2 minutes. Remove from the heat.
Place the blueberries and peaches in a mixing bowl and pour the syrup over the peaches. Toss well and cool for 10 minutes.
In a mixing bowl, combine the remaining 1/2 cup brown sugar, remaining 1/4 teaspoon cinnamon, remaining 1/4 teaspoon nutmeg, flour, oatmeal, and butter. Using your fingers, work the mixture together until it resembles a coarse crumb-like mixture. Pour the fruit mixture into the prepared pie shell. Sprinkle the topping over the top of the fruit filling. Bake for 1 hour, or until the crust is golden. Remove the pie from the oven and cool for 15 minutes before slicing.
Slice and serve warm. Garnish with the sweetened whipped cream, fresh mint and powdered sugar.
Yields: 8 servings