Preheat the oven to 400 degrees F. For the muffins: Combine the dry ingredients in a large bowl. In a small bowl, combine the egg and the milk and then add this mixture to the dry ingredients along with the melted butter. Stir until just moistened and the fold in the blueberries. Fill greased or paper-lined muffin cups 2/3 full. For the topping: Combine the topping ingredients and sprinkle over the batter. Bake at 400 degrees F for 16-20 minutes or until browned and springy or a toothpick that doesn't hit a blueberry comes out clean. Cool a few minutes in the pan and then remove to a wire rack.