Preheat oven to 375°. Place butter in an 8-inch square baking dish; place dish in oven just until butter melts. Remove from oven, and cool 10 minutes.
Combine flour, sugar, baking powder, and salt in a large mixing bowl; add milk, and mix well. Pour batter into prepared baking dish; sprinkle blueberries over batter. Bake at 375° for 30 minutes or until golden brown. Spoon dessert into individual serving dishes; serve warm with whipped cream.