Combine flour, 3/4 cup of sugar, and baking powder, then mix thoroughly. Add milk, butter, and vanilla and mix gently until just combined. Spoon the batter over the blueberries.
1 cup flour, 3/4 cup sugar, 1 teaspoon baking powder, 1/2 cup milk, 3 tablespoons unsalted butter, 1/2 teaspoon vanilla
Mix remaining 3/4 c sugar and cornstarch. Sprinkle over the batter. Pour boiling water over the entire cake.
3/4 cup sugar, 1 tablespoon cornstarch, 1 cup boiling water
Bake at 350 degrees for 45 minutes or until cake tester comes out clean.