Preheat the oven to 400 degrees F.
In a food processor, combine the flour, baking powder, salt and butter. Pulse until the mix clumps together to form larger pea-size balls. Drizzle in the buttermilk until the dough come together and looks rough. The dough will be a little dry.
Turn the dough out onto a clean surface and pat into 1-inch thick square. Cut the dough into 4 pieces. Stack the pieces on top of each other. Press down to flatten. Dust the surface with flour and roll the dough into a 1 inch thick rectangle. Cut into 12 biscuits. Transfer to a parchment-lined baking sheet and chill in the freezer for 10 minutes.
Combine half of the fruit mixture and sugar in a skillet set over high heat. Bring the fruit to a boil and cook 5-10 minutes, until their juices are bubbling. Remove from heat. Add the remaining fruit, cornstarch, zest and vanilla and toss to combine.
Remove the biscuits from the freezer, brush with milk. Pour the fruit mixture into a 9x13 inch baking dish. Arrange the biscuits on top. Place the baking dish on a baking sheet. Bake for 35-40 minutes, until golden on top. Let cool 5 minutes. Serve warm or at room temp with ice cream.