Ingredients

For the cake

2 1/2 cups biscuit mix (like Bisquick)
1/2 cup sugar
1 cup blueberries
1/2 cup sour cream
2 eggs
3 tbsp. milk
1/2 tsp. vanilla extract
Crumb Topping
1/2 cup sugar
1/3 cup flour
4 tbsp. butter (cut into small cubes)

Preparation

Preheat oven to 350°F degrees
    
Spray 9x13 baking dish with nonstick cooking spray (I like the kind that has flour in it)
    
In a medium bowl combine biscuit mix and sugar. Add sour cream, eggs, milk and vanilla extract. Mix until combined. Batter will be very thick. Gently stir in blueberries by hand. This will take a few minutes because batter is thick.
    
Scoop batter into prepared baking dish and make sure it is evenly spread.
    
In a bowl, combine sugar, flour and butter. Using your fingers or a pastry cutter, start combining mixture until it looks coarse and crumbly.
    
Sprinkle mixture over dough.
    
Bake about 30-35 minutes until a toothpick inserted comes out clean.

Formulation courtesy of BigOven