Preheat oven to 375 degrees. In a large bowl, combine the sugar and butter, creaming until light. Add the egg, mixing well.

In a separate bowl, combine the flour and baking powder. Add the dry ingredients to the creamed mixture alternately with the milk, stirring well after each addition. Stir in vanilla and blueberries.

Spoon into muffin pans lined with muffin cups, filling each 2/3 full. Sprinkle Streusel Topping over muffins. Bake for 25-30 minutes or until done. Makes 16-18 muffins.