Heat oven to 375°. Toss fruit filling ingredients together in mixing bowl. The filling should be fairly soupy. If too dry, add more vanilla and bourbon in equal parts. Pour filling into 9- by 12-inch baking dish. Place on a baking sheet and bake uncovered 35–40 minutes, gently stirring every 15 minutes. This will help the cornstarch to cook evenly and the juices to become translucent.
Meanwhile mix the flour, baking powder and salt together in a bowl and set aside. Beat butter and sugar with an electric mixer on medium speed until light and fluffy (about 3 minutes). Beat in egg and vanilla until smooth. Stir in dry ingredients until just combined. Spoon topping evenly over hot filling (or use a piping bag with a large tip). Return to oven and bake until topping has spread and is nicely browned and fruit is bubbly (about 45 minutes). Enjoy!
Recipe by Owners Jennifer Gibson & Andrew Nathan, The Cooked Goose, Watch Hill