Use frozen peaches and raspberries without thawing; add 1 extra tbsp cornstarch if your fruit is very juicy. For a gluten-free version, use a cup-for-cup gluten-free flour blend. If you prefer a less sweet cobbler, reduce the filling sugar to 0.33 cup. Leftovers keep covered in the fridge for 3 days; rewarm in a 325°F oven until heated through.