6 tbsp. butter, softened
1 lg. egg
3 tbsp. cornstarch
1/4 tsp. salt
1/2 c. milk
3/4 c. sugar
2 c. all-purpose flour
2 tsp. baking powder
1 tsp. vanilla
2 c. fresh blueberries

Preheat oven to 375 degrees. In a large mixer bowl, cream the softened butter; add the sugar a little at a time and beat until mixture is light and fluffy. Add the egg and beat well. Sift together the flour, cornstarch, baking powder, and salt; add to the butter mixture, alternating with the combined milk and vanilla, with the mixer on low speed. Stir in the blueberries by hand. Spread the batter evenly in an oiled 8-inch-square cake pan. Spoon the topping evenly over the batter; bake for 40 to 45 minutes. Let cake cool for 15 minutes. Cut squares and serve warm.

TOPPING:

1/4 c. granulated sugar
1/3 c. all-purpose flour
1/4 tsp. ground mace
1/4 c. brown sugar
1/2 tsp. ground cinnamon
1/4 c. butter, cold