Instructions

• Preheat the oven to 375°F. Grease a skillet with 1 teaspoon unsalted butter (at room temperature).
• Place 5 cups frozen unsweetened mixed berries in the greased skillet. Drizzle 1 tablespoon freshly squeezed lemon juice over the berries and spread them into an even layer.
• In a small bowl, whisk together 2/3 cup granulated white sugar and 2 tablespoons cornstarch until combined. Sprinkle this mixture evenly over the berries and gently stir once or twice to coat.
• In a medium bowl, combine 1 cup all-purpose flour, 2/3 cup packed dark brown sugar, 1 teaspoon ground cinnamon, and 1/4 teaspoon salt; mix to combine.
• Add 1/2 cup (1 stick) cold unsalted butter, cubed, to the flour mixture. Using a pastry blender, two knives, or your fingertips, cut the butter into the dry ingredients until pea-sized pieces remain. Then use your fingertips to press and pinch the mixture into larger clumps to form the crumble topping.
• Sprinkle the crumble topping evenly over the berry layer, covering as much of the berries as possible.
• Bake in the preheated oven for 45 to 60 minutes, or until the topping is golden brown and the fruit filling is bubbling.
• Remove the skillet from the oven and place it on a wire rack. Let the crumble cool for 15 minutes.
• Spoon the crumble into individual serving bowls and top with vanilla ice cream, if using.