Heat oven to 375° F. Butter an 8-inch square baking dish.
Add the berries and 1 1/2 tablespoons of the sugar to the dish and toss. In a large bowl, combine the pancake mix, milk, and eggs until no lumps remain. Pour the batter over the berries. Bake until the crust is golden and a toothpick inserted in the center comes out clean, about 30 minutes. Remove from oven. Let cool for 5 minutes. Sprinkle with the remaining sugar and serve with a dollop of whipped cream.