1 1/2 c. Bisquick baking mix
1/2 c. sugar
2 tbsp. softened butter
1 egg
3/4 c. dairy sour cream
1 tsp. vanilla

Mix cake ingredients and stir vigorously about 1 minute. Spread in 8 x 8 x 2 baking dish; sprinkle streusel over top.

STREUSEL:

1/4 c. flour
3 tbsp. sugar
1/8 tsp. cinnamon
2 tbsp. firm butter

Mix until crumbly.

Bake in 350 degree oven about 35 minutes or until pick inserted in center comes out clean. Cool 10 minutes and cut into squares.