8tablespoonsbutter, unsalted, chilledcut into 1/2 inch pieces
2cupshalf and half, chilled
Preheat the oven to 500 ºF
Place the flour, baking soda, cream of tartar and sugar into the bowl of a food processor. Process briefly to combine.
Add the chilled butter and process off and on until the butter is finely cut into the dry ingredients.
Turn the mixture out into a large bowl and gradually add the chilled cream, cutting through the mixture with a large fork to combine. Do not stir the dough, or your biscuits will be tough.
Add enough half and half to make a soft dough. You may need a little more or a little less than 2 cups, depending on how dry your flour is.
Turn the dough out onto a floured surface and gently knead the dough five or six times. Re-dust the surface with flour if needed, and roll the dough to 1/2 inch thick. Use a 3-inch cutter to make the biscuits.
Place biscuits on an unlined baking pan. If you would like the surface to have a sparkled effect, lightly brush the tops of the biscuits with just a bit of half and half, and sprinkle some sugar on them. Otherwise, bake them plain. (They will rise a bit more if you do not brush and sprinkle them.)
Immediately bake the biscuits on the middle rack of oven for 9-12 minutes, until golden brown.