1/4 cup butter, room temperature
Cream 1/4 cup butter with 3/4 cup sugar; add egg and beat well. Into a medium bowl sift together 2 cups flour, baking powder, and salt. Add sifted dry ingredients to butter mixture alternately with 1/2 cup milk, beating until smooth. Fold in blueberries. Pour into a greased 9-inch square baking pan. For topping, combine blend together ingredients.
Sprinkle topping crumbs over batter. Bake at 375° for 35 minutes.