Image credit to: Beth Harris
Preheat oven to 375 degrees, with racks in middle and lower thirds. In a large bowl, whisk together cornstarch and 1/2 cup granulated sugar. Stir in apricots and blueberries. Spread mixture into a 10-inch cast-iron skillet or 9x13 baking dish.
In food processor, pulse remaining 2 Tbsp granulated sugar, flour, baking powder, and salt until combined. Add butter and pulse until mixture resembles coarse meal, with a few pea-size pieces of butter remaining. Add heavy cream and pulse 2 or 3 times until combined.
Spoon batter in 8 mounds on fruit mixture. Press lightly on tops to flatten, brush with heavy cream, and sprinkle with sugar if desired.Bake on middle rack, with a foil-lined rimmed baking sheet on lower rack to catch drips, until biscuits are golden and juices bubble in center, 20-30 minutes.
Transfer to a wire rack and let cool. Serve warm or at room temperature.