Preheat your oven to 400°
Combine the flour, sugar, baking powder, baking soda and salt in a large bowl or food processor, if using. Whisk or pulse to combine.
Add the cold cubed butter to the dry ingredients and cut in with a pastry blender or pulse a few times until you get coarse crumbs.
If using a food processor, pour the butter and dry ingredient mixture into a large bowl.
Add the buttermilk onto the crumb mixture and fold everything together with a wooden spoon or large spatula until it starts to come together. Do not overwork it. The dough will be shaggy.
Pour the dough and crumbles out onto a lightly floured work surface and gently bring it together. If it sticks to your hands, lightly flour them.
Using a lightly floured rolling pin, or your hands, flatten the dough into a ¾" thick rectangle then fold one side into the center then repeat with the other side (you will have 3 layers). Turn the dough 90° and flatten to ¾" thick again then repeat the folding process, turn 90° and again flatten to ¾" thick rectangle.
Cut the biscuits into 2.5 to 3" circles (do not twist your cutter).
Re roll any scraps and cut out until you have 10-12 biscuits
Arrange the biscuits into a lightly buttered (or oiled) cast iron skillet making sure they touch. If you are not using a cast iron skillet then put the biscuits on a parchment lined baking sheet once again, making sure they are touching as much as possible.
Lightly brush the tops with either the heavy cream or buttermilk, then sprinkle with the coarse sugar.
Bake for 20 minutes or until biscuits are a light golden brown on top. Remove from the oven and let them cool in the pan for 10 minutes. If you assemble them too warm, the whipped cream will melt.