Heat oven to 375°F (190°C). Butter a 9-inch square baking pan.
To Prepare The Cake:
In large mixer bowl, beat butter and sugar until well blended. Add milk and egg. In small bowl, combine flour, baking powder and salt. Add to butter mixture; stir just until combined. Fold in blueberries. Pour batter into buttered pan.
To Prepare The Topping:
Combine all topping ingredients in food processor bowl with metal blade; process until combined. Sprinkle evenly over batter.
Bake at 375°F (190°C) for 45 to 50 minutes or until toothpick inserted in center comes out clean. Cool 20 to 30 minutes before serving.
Makes: 9 servings