Wash hands with soap and water for 20 seconds.
Donot taste or eat any raw dough or batter made with uncooked flour and/or raw eggs.
Place a rack in the upper-middle position of the oven and preheat to 500°F.
Grate frozen butter.
Make your own levening by sifting together the cream of tartar and baking soda.
In a large bowl, whisk together the cream of tartar, baking soda, flour, and salt. Add the grated butter and freeze the bowl for at least 20 minutes. Quickly work the pieces of butter into the flour with a pastry cutter or rub it between your fingertips until coarsely blended lumps form.
Make a well in the center of the bowl and pour in the chilled buttermilk. Quickly mix the ingredients until the mixture just comes together and forms a shaggy mass. Add 1-2 more Tablespoons of buttermilk if the mixture seems dry.
Immediately turn the dough out onto a generously floured surface and quickly knead the dough about ten times until a ball forms. Gently flatten the dough out to a 3/4-inch thickness.
With a fork that has been dipped in flour, pierce the dough at half-inch intervals. Flour a 2 1/2 or 3-inch biscuit cutter, and stamp out biscuits as close together as possible, taking care not to twist cutter. When you have run out of room to stamp out more biscuits, carefully reform the dough and press out as many biscuits as you can one more time.
Arrange the biscuits so they almost touch on a parchment-lined baking sheet.
Bake until golden, about 10-12 minutes. Remove from the oven and brush the tops with the melted butter. Serve warm with butter, honey, and/or jam.