Ingredients

For the crumble topping:

• 8 tablespoons (1 stick) unsalted butter, melted and cooled, plus more for the baking dish
• 1 cup all-purpose flour
• 1/2 cup packed light or dark brown sugar
• Finely grated zest of 1 medium lemon (about 1 tablespoon)
• 1 teaspoon vanilla extract
• 1 teaspoon baking powder
• 1/2 teaspoon kosher salt

For the berry filling:

• 6 cups fresh or thawed frozen mixed berries, such as blackberries, blueberries, and raspberries (about 26 ounces)
• 1/4 cup granulated sugar
• 3 tablespoons cornstarch
• 1 teaspoon vanilla extract
• 1 teaspoon ground coriander, cardamom, or cinnamon (optional)
• 1/2 teaspoon kosher salt
• Vanilla ice cream, for serving (optional)

Make the crumble topping:

1. Heat the oven to 375°F. Coat an 8x8-inch or 2- to 2 1/2-quart baking dish with butter.
2. Stir 1 stick melted unsalted butter, 1 cup all-purpose flour, 1/2 cup packed brown sugar, the finely grated zest of 1 medium lemon, 1 teaspoon vanilla extract, 1 teaspoon baking powder, and 1/2 teaspoon kosher salt together in a medium bowl with a fork until evenly moistened and a variety of crumb sizes form. The mixture will be thick and slightly pasty. Refrigerate until firm, about 10 minutes.

Make the berry filling:

1. Drain the liquid from the thawed berries if needed. Stir 6 cups mixed berries, 1/4 cup granulated sugar, 3 tablespoons cornstarch, 1 teaspoon vanilla extract, 1 teaspoon ground spice if using, and 1/2 teaspoon kosher salt together in a large bowl.
2. Transfer to the baking dish and spread into an even layer. Break the crumble topping into large clumps with your hands and scatter over the filling in an even layer.
3. Bake until the juices are bubbling around the edges and the topping is golden-brown and firm to the touch, 40 to 45 minutes. Check at 30 minutes — if the topping is browned, tent with aluminum foil for the remainder of time. Let cool for at least 15 minutes before serving with vanilla ice cream if desired.