Preheat the oven to 400℉ (205℃).
In a large mixing bowl, whisk the flour, baking powder, baking soda, sugar, and salt.
Grate the butter into the flour mixture quickly until it resembles coarse crumbs. Or cut the cold butter into the flour mixture with a pastry blender until the mixture resembles coarse crumbs; this might take about 5 minutes.
Make a well in the center of the flour mixture, add the buttermilk, and stir with a spoon until it forms a rough ball—avoid overmixing. Let it rest in the fridge for about 10 minutes. That gives the butter a chance to firm back up.
Turn the dough out onto a floured surface and knead it 3-4 times, just enough for it to come together.
Cut the dough into 4 pieces, gently roll them out, stack them, and roll them out again. Repeat, cutting the dough into 4 pieces, rolling them out, stacking them, and then rolling them out again to ½-1 inch thick. That will give you the flaky layers.
Use a 2-inch round cookie cutter or drinking glass to cut out the biscuits, and space them evenly on your prepared baking sheet. (My pictures show 9, but you can knead the scraps and roll them out to make the other 3 for a complete dozen. They're just not as pretty.)
Brush with cream and bake at 400℉ (205℃) for 12-15 minutes or until lightly browned.
Remove from the oven and serve warm.