Cream the margarine & sugar together in a mixing bowl.
Add the vanilla & eggs slowly to the mixture.
Sift in the flour, baking powder and cocoa.
Fold in the blueberries and bake for 20 - 30 minutes or until set.
Remove, cool and cut up into slices.
Serve with whipped cream and sliced bananas.
350g caster sugar
1 teaspoon of vanilla essence
125g plain flour
1 teaspoon of baking powder