Preheat oven to 375°. Prep your berries. Blackberries or raspberries or any mixture should be fine.
First, test taste your fruit. If very sweet or tart, then you will need to adjust the sugar. Combine 1/4 cup white sugar (depending on sweetness), 2 teaspoons cornstarch (3 teaspoons if using frozen fruit which is generally watery) and 1/8 teaspoon kosher salt.
Toss berries gently with sugar mixture.
Divide the berries into two bowls 10 to 12 oz size.
Combine 1/2 cup flour, 1/3 cup rolled oats (not quick), 1/4 cup brown sugar and 1/4 teaspoon cinnamon.
Chop 4 tablespoon firm butter into small pieces and "cut" into the topping mix until the crumble is formed.
Divide the topping over the two bowls.
Bake until the top is golden brown. About 25 to 30 minutes. Cool on a rack for about 10 minutes and serve.