Adjust oven rack to middle position and preheat oven to 425 degrees F.
Put flour, sugar, baking powder, and salt into the bowl of a food processor, and pulse about 6 times to mix.
Scatter the pieces of butter over the dry mixture and pulse until the mixture resembles coarse cornmeal with a few slightly larger clumps of butter, about 12 pulses more.
Transfer the mixture to a large bowl and stir in the currants. Stir in the heavy cream with a rubber spatula for about 30 seconds until dough forms.
Transfer the dough to a lightly floured work surface and knead by hand just until the dough comes together into a sticky ball, about 5 to 10 seconds.
If making regular sized scones:
Flatten the dough into a disc and cut into 8 even wedges. Place the dough onto an ungreased baking sheet. It can be baked immediately or covered in plastic wrap and be refrigerated for up to 2 hours. Proceed to glaze step.
If using mini scone pan:
Spray with cooking spray containing flour (or grease with shortening and dust with flour per pan instructions). Press dough evenly into the wells of the pan.
To add glaze, brush the tops of the scones with heavy cream and sprinkle with sugar.
Bake until the scone tops are light brown, 12 to 15 minutes for regular sized scones, a bit less for mini scones. Cool on a wire rack for at least 10 minutes.