Ingredients: 

1/2 cup butter or 1/2 cup margarine, at room temp

1 cup granulated sugar
2 large eggs
1 teaspoon vanilla
2 teaspoons baking powder
1/4 teaspoon salt
2 cups all-purpose flour
1/2 cup milk
2 1/2 cups fresh blueberries or 2 1/2 cups frozen blueberries

Directions:
1 Heat oven to 375°.
2 Grease 18 regular-size muffin cups (or 12 large size muffins).
3 In bowl, mix butter until creamy. Add sugar and beat until pale and fluffy.
4 Add eggs one at a time, beating after each.
5 Beat in vanilla, baking powder and salt.
6 With spoon, fold in half of flour then half of milk into batter; repeat.
7 Fold in blueberries.
8 Spoon into muffin cups and sprinkle topping onto each muffin.
9 Bake 15 to 20 minutes, until golden brown and springy to touch.

Credits to/Entire Recipe From: http://www.food.com/recipe/the-best-blueberry-muffins-50719