In a bowl, combine the dry ingredients. Combine egg and milk. Add egg mixture and butter to dry ingredients; stir just until moistened. Fold in blueberries.
Fill greased or paper-line muffin cups two-thirds full. Combine the topping ingredients; sprinkle over batter. Bake at 400 degrees F or 205 degrees C for 16-20 minutes or until a toothpick comes out clean.
Cool for 5 minutes before removing from pan to a wire rack.