1. Bake the empty prepared pie crust according to package directions. Let cool on a wire rack.
2. In a small bowl, whisk together the water and cornstarch into a slurry. Set aside.
3. Heat a medium sized skillet over medium-high heat. Add the peaches, sugar and lemon juice.
4. Stir the slurry into the peaches until combined. Bring to a boil, stirring until the mixture has thickened.
5. Remove from the heat and let cool to room temperature. Once cool, stir in the raspberries until coated, then pour the mixture into the prepared crust. Garnish the pie with mint leaves.
6. Refrigerate until chilled, at least 6 hours. Serve cold.