Preheat your oven to 375°F (190°C) and grease a 9×13-inch baking dish with butter or non-stick cooking spray.
In a large mixing bowl, combine the mixed berries, granulated sugar, cornstarch, lemon juice, and vanilla extract. Gently toss until the berries are evenly coated. Pour the mixture into the prepared baking dish, spreading it out into an even layer.
Make the Cobbler Topping:
In a separate mixing bowl, whisk together the flour, granulated sugar, baking powder, and salt until well combined.
Add the cold butter pieces to the flour mixture. Using a pastry cutter or your fingers, work the butter into the flour until the mixture resembles coarse crumbs.
Pour the boiling water over the flour mixture and stir until a thick batter forms.
Assemble and Bake:
Drop spoonfuls of the cobbler batter over the berry filling in the baking dish, covering it as evenly as possible.
Place the baking dish on a baking sheet (to catch any drips) and transfer it to the preheated oven.
Bake for 35-40 minutes, or until the cobbler topping is golden brown and the berry filling is bubbly.
Remove the cobbler from the oven and let it cool for 10-15 minutes before serving.
Serve and Enjoy:
Scoop generous portions of the warm mixed berry cobbler into serving bowls.
Serve with a dollop of vanilla ice cream or whipped cream, if desired.
Enjoy the delightful combination of sweet, juicy berries and tender cobbler topping with friends and family!
