Sour Cream Blueberry Muffins

1 stick softened butter
1 c. sugar
2 eggs
2 c. flour
1 tsp. baking powder
1 tsp. baking soda
1/4 tsp. salt
1 tsp. vanilla
1 c. sour cream
1 3/4 c. blueberries

Topping:
1/2 c. sugar
1/3 c. flour
1/2 tsp. cinnamon
1/4 c. soft butter

Cream butter and sugar. Beat in eggs until creamy. Add dry ingredients alternately with sour cream. Stir in blueberries and vanilla. Fill muffin cups 2/3 full and sprinkle a heaping teaspoon (or more) topping. Bake at 350 degrees for 25-30 minutes. Makes 24.