In a saucepan, add the blackberries, cornstarch, sugars, lemon juice and cinnamon. Mix together and place over medium heat.Stir occasionally until the black berries break down and everything becomes a thick sauce. (About 8 minutes) Be sure to watch over the mixture, so the berries don't start burning and stick to the bottom of the pan. Preheat the oven to 350 degrees F.
Pour the blackberry filling into a baking dish.
In a mixing bowl, add the flour, cinnamon, baking powder and salt. Mix together with a fork.
Add the softened butter and blend with the dry ingredients.
Then add the brown sugar and granola, mixing once again until combined and crumbly.
Place the crumble topping all over the top of the blackberry filling.
Bake for 25 minutes until the filling is bubbling through the crust.
Let cool for a couple minutes. Top with a couple scoops of ice cream and extra blackberries.
Enjoy!