1-Begin by preheating your oven to 350°F (175°C) and greasing a 9×13-inch baking pan to avoid any sticking issues.

2-In a large bowl, gently combine 8 cups mixed berries with 1/2 cup granulated sugar, 2 tablespoons cornstarch, 1 teaspoon lemon juice, and 1/2 teaspoon pure vanilla extract, then spread the mixture evenly in the prepared pan.

3-In another bowl, whisk together 1 1/2 cups all-purpose flour, 1/3 cup granulated sugar, 1 1/2 teaspoons baking powder, and 1/4 teaspoon salt.

4-Cut in 6 tablespoons of cold unsalted butter, cubed, until pea-sized crumbs form, then gradually stir in 1/2 cup cold buttermilk until the dough comes together.

5-Flatten the dough into sections with your hands and place it over the berry mixture in the pan.

6-Brush the biscuit dough with 1 tablespoon buttermilk and sprinkle with coarse sugar.

7-Bake for 45-55 minutes until the biscuit topping is golden brown and cooked through. Let it cool for 5 minutes before serving warm, and consider adding a scoop of vanilla ice cream for extra enjoyment.