Preheat oven to 400 degrees.
In a large mixing bowl, combine the berries, sugar, cornstarch, lemon juice, lemon zest, and vanilla extract. Set aside.
Meanwhile, in a large mixing bowl, whisk together the flour, sugar, baking powder, and salt. Add the cold cubed butter. With a pastry blender, work until mixture becomes sandy. Pour in the heavy cream and mix until the dough becomes moist and no loose pockets of flour remain.
Divide the dough into thirds and shape into biscuits approximately 6.5-inches in diameter and 1/2 inch thick.
Divide the berries in between the three 6.5-inch cast iron skillets. Top with a biscuit, pressing the edges to the sides of the skillet to seal in the berries.
Brush the tops with heavy cream, then sprinkle with coarse sugar.
Place in the oven and bake for 18-22 minutes or until the tops of the biscuits are golden brown in color.
Carefully remove from the oven and allow to cool for 10 minutes before serving. Top with ice cream or whipped cream, extra berries and a sprig of mint, if desired.