Prep time: 15 minutes
Total time: 45 minutes
2 3/4 pounds|1.25 kg peaches, pits removed and sliced into 1/2-inch wedges
2 pounds|835 grams blueberries (about 3 pints)
¾ cup|190 grams granulated sugar
2 tablespoons cornstarch
3/4 cup|95 grams all-purpose flour
1/2 cup|50 grams rolled oats
1/4 cup|45 grams light brown sugar
6 tablespoons|85 grams unsalted butter, cold
vanilla ice cream, for serving
1. In a large bowl, toss the peaches and blueberries with 1/2 cup of the granulated sugar and the cornstarch. Set aside.
2. In a medium bowl, toss the remaining ¼ cup of granulated sugar with the flour, oats, brown sugar, and the butter. Use your fingers to break up the butter into pea-sized crumbles. Keep the crumbs refrigerated until ready to use.
3. Light a grill. Heat a large cast-iron skillet directly on the coals. Add the crumbs and cook, stirring constantly, until golden, about 15 minutes. Transfer the crumbs to a bowl.
4. Add the peaches and berries and cook, stirring occasionally, until the berries have popped and the peaches are soft, about 10 minutes. VERY CAREFULLY remove the skillet from the coals and transfer to a safe place. Top with the crumble and serve with vanilla ice cream on top.
COOK'S NOTE: You can totally make this in the oven or on the stovetop. To do it on the stovetop, do it the exact same way over medium-high heat. To bake it, heat the oven to 375°F. Toss the peaches and blueberries with 1/2 cup sugar and the cornstarch in a large bowl. Transfer to a large cast-iron skillet, then top with the uncooked crumbs. Bake until the crumbs are golden and the fruit is soft and bubbling, about 50 minutes.