Preheat oven to 375°F and grease a 9x13-inch baking dish.
In a large bowl, combine strawberries, peaches, 3/4 cup sugar, cornstarch, and vanilla extract. Pour into prepared baking dish.
In a separate bowl, whisk together flour, 1/2 cup sugar, baking powder, and salt. Cut in cold butter using a pastry cutter or fork until mixture resembles coarse crumbs.
Pour boiling water over the flour mixture and stir just until combined. Drop spoonfuls of batter over the fruit filling.
Bake for 40-45 minutes until topping is golden brown and fruit is bubbling around the edges.
Let cool for 15 minutes before serving warm with ice cream or whipped cream.