1. With the rack in the middle position, preheat the oven to 350°F (180°C).
2. In a large bowl, combine the sugar and cornstarch. Add the fruits and toss to coat well. Spread out in an 11 x 8-inch (28 x 20 cm) glass baking dish.
3. In another bowl, combine the butter and ground almonds with your fingertips. Add the remaining ingredients and mix until the dry ingredients are moistened and the mixture comes together when pressed between your fingertips. Spread the crumble over the fruit.
4. Bake for 50 minutes or until the fruit is bubbling and the crumble is golden. Let cool for 1 hour before serving. Delicious served with vanilla ice cream.

Chef’s tip : The apple adds texture to the crisp without changing the flavour. The rhubarb breaks down into a compote as it bakes, especially if using frozen rhubarb.