Preheat oven to 400 degrees F. Spray a 10" cast iron pan with non-stick spray and set aside.
Peel peaches and slice. Cut strawberries and remove stems off blueberries. Toss fruit together in a medium sized bowl. In a small bowl, whisk together sugar and cornstarch. Sprinkle on fruit. Add in vanilla and stir until combined. Set aside while you prepare the crust.
Use your favorite homemade pie crust or use a shortcut version like the boxed Krusteaz mix I used. It tastes delicious, is easy to work with and you simply add water and stir. Easy! Roll out 1/2 the pie crust until it's about 11" in diameter. Transfer to cast iron pan and smooth dough into pan and up around the edges.
Roll remaining pie crust and cut 12-15 small shapes using cookie cutters. You're welcome to use whatever shapes you'd like!
Pour prepared fruit into crust. Place pie crust shapes around edges. Fold the tops of the bottom crust over onto the shapes, if there's excess. Brush crust with a beaten egg, if desired. (It adds a lovely sheen.)
Bake pie at 400 degrees F for 50 minutes. Let cool about 30-45 minutes, then slice and serve with vanilla ice cream. Store Berry Peach Pie leftovers in an airtight container in the fridge.