Preheat oven to 375 degrees F.
Add the peaches, blackberries, basil (if using), sugars, cinnamon, vanilla, cornstarch, and lemon juice to a sauce pan. Stir to coat the peaches. Bring to a boil and let cook for 1-2 minutes. Remove from heat and set aside.
To a bowl, add the flour, baking powder, sugar, cinnamon, and salt. Whisk to combine. Add the milk and egg. Whisk until it creates a smooth batter.
Add the melted butter to the baking dish. Pour the batter directly on top of the butter, making sure to NOT STIR IT.
Spoon the fruit filling and their juices on top of the batter. DO NOT STIR IT.
Bake in the preheated oven for 45-55 minutes, or until the top is golden and the middle is set. Serve with vanilla icecream if desired.