Heat the oven to 475°F with a rack in the middle position. Line a baking sheet with kitchen parchment. In a large bowl, whisk together the flour, 1 tablespoon of sugar, the baking powder, salt and baking soda.

In a second large bowl, use a whisk or electric mixer to beat the cream and sour cream to soft peaks; set aside. Scatter the butter cubes over the flour. With your fingertips, rub together until the butter is thoroughly and evenly dispersed in the flour.

Add the whipped cream mixture to the flour mixture. Use a large rubber spatula to fold and press until large clumps form and no dry flour remains.

Use your hand to knead the dough in the bowl until it forms a shaggy mass, adding additional cream 1 tablespoon at a time, if needed.

Turn the dough out onto a lightly floured counter and divide in half. Form each piece into a rough 5-inch square about ¾-inch thick.

With a bench scraper or chef’s knife, cut each square into 4 pieces. Evenly space the biscuits on the prepared baking sheet. Brush the tops with the melted butter and sprinkle with the remaining ½ tablespoon sugar.

Place the baking sheet in the oven and immediately reduce the temperature to 425°F. Bake until golden brown on top and bottom, 15 to 18 minutes, rotating the pan halfway through. Let cool on the baking sheet for 10 minutes.