For these unusual brownies, you need to make the apple crumble first. Then you prepare your brownie mixture and layer the brownie, dividing the mixture in two so that you have the first half, then the apple crumble on top, finished with the final layer of brownie mixture. The result is delicious gooey brownies with that apple crumble surprise in every bite. Serve them on their own, with cream, with ice cream or maybe even custard.