Preheat your oven to 375°F (190°C). Lightly butter or spray a 9-inch (or similar) baking dish.

If you prefer an extra-crispy edge, use a cast-iron skillet.

In a large bowl, toss sliced peaches and blueberries with sugar, lemon juice, cornstarch, vanilla, and a pinch of salt. Let sit for 10 minutes to macerate.

If the fruit releases a lot of juice, that’s okay — the cornstarch will thicken it while baking. For slower juicing, reduce maceration time to 5 minutes.

In a bowl, combine oats, flour, brown sugar, cinnamon, nutmeg, and nuts (if using). Cut cold butter into the mixture until pea-sized crumbs form.

You can also pulse 6–8 times in a food processor.

For a chewier crumble, mix in 2 tbsp honey or maple syrup.

Pour the fruit mixture into the baking dish and spread evenly. Sprinkle the crumble topping evenly over the fruit, pressing lightly so it adheres in places.

For individual portions, divide into ramekins and shorten bake time by 5–7 minutes.

Bake at 375°F for 30–35 minutes, until the topping is golden and fruit is bubbling at the edges.

If the topping browns too quickly, loosely tent with foil for the last 10 minutes.

Let the crumble rest 10–15 minutes before serving so the filling sets slightly.

Pair with vanilla ice cream or a dollop of crème fraîche.