Add the strawberries and mango to a medium-sized casserole dish.

In a bowl, combine the brown sugar, cornstarch, and flour. Stir the dry ingredients to combine and sprinkle over the fruit. With a big spoon, stir fruit around so that it is coated with the dry mixture. Set aside.

Preheat the oven to 350 degrees.

Add the brown sugar, flour, salt and baking powder to a mixing bowl and stir.

Integrate the cold butter by pressing it with your hands into the flour mixture. Once the flour mixture resembles small beads with the butter incorporated, pour in the oats and stir. Drizzle the tablespoon of water into the mixture and still using your hands, make sure the crumble is thoroughly mixed.

Spread the crumble topping evenly over the fruit and bake in the oven for 35 to 40 minutes until the fruit juices bubble up and topping is slightly browned.

Allow the crumble to cool about 10 minutes and serve with huge scoops of vanilla gelato (or frozen yogurt or ice cream).