In a medium-sized bowl, combine the apple pieces and the berries and toss with the 1-3 tablespoons of sugar and cinnamon. Transfer the apple mixture to a 14x25-cm/5.5-10-inch (or similar) oven dish.
In a small bowl, combine the cold butter cubes, the remaining sugar, flour, salt and baking powder. Using your fingertips, rub the ingredients together until fine crumbs form. Add the rolled oats and crushed Biscoff cookies and stir with your hands until combined. Sprinkle the crumble mixture in an even layer over the fruit.
Bake the crumble on a rack in the middle of the oven until golden and bubbly, about 55-65 minutes. Remove from the oven and allow to cool slightly before serving. Serve as it is or with some whipped cream or ice cream.
Recipe by The Tough Cookie at https://thetoughcookie.com/2015/11/17/apple-and-mixed-berry-crumble-with-biscoff-cookies/