Blackberry Crumble - cooking recipe

Ingredients

2 qt. blackberries or plums (fresh or frozen)
2 c. sugar
5 Tbsp. cornstarch
1 tsp. vanilla
1 c. margarine or butter
1 1/2 c. brown sugar
1/2 tsp. salt
2 c. uncooked oatmeal
1 1/2 c. flour
1 tsp. baking powder

Preparation

Cook first 4 ingredients together until thick.
It may be necessary to break fresh berries to produce juice.
Set aside this filling mixture.