Preheat the oven to 220 C (425 F).
Mix together the flour, sugar, baking powder and salt in a large bowl or in the bowl of a food processor.
Add the cubed butter either by rubbing it into the flour with your hands, or pulsing with a food processor (I find this much easier) until coarse crumbs form.
If you used the food processor, tip the crumbs out into a large bowl. Pour the 1 cup of heavy cream or buttermilk on top. Stir until just combined.
Place dough onto a lightly floured work surface and use your hands to knead the dough a little till it comes together into a shaggy, slightly sticky dough.
Roll dough out or pat it out with your hands until it is 1/2 inch thick. Use a 3 inch biscuit cutter and cut out dough circles. You can reshape leftover dough scraps to continue cutting out biscuits. You should get around 12 biscuits. You can also use a sharp knife and cut squares out of the dough if you don't have a biscuit cutter.
On a parchment paper lined baking sheet, place the dough circles. Brush with some heavy cream, buttermilk, or melted butter and sprinkle with coarse sugar.
Bake for 12-15 minutes or until biscuits are a nice golden brown on top. Cool 10 minutes before assembling, and prepare whipped cream while cooling.