Preparation

1. Preheat oven to 190° C (375° F). Place the butter in the freezer while preparing the rest of the ingredients; the key to fluffy biscuits is very cold butter.

2. In a large bowl, sift together the flour, baking powder, salt, sugar, and baking soda; set aside.

3. Using the large holes of a box-style grater, quickly grate the butter onto a plate or sheet of wax paper. To keep the heat of your hands from softening the butter, you may want to hold it with a paper towel. Place the grated butter back into the freezer until very well-chilled again, for another 15 to 20 minutes.

4. Add the buttermilk to the dry ingredients, mix lightly, and add the butter. Mix by hand, breaking up the butter and smoothing it into the flour. The finished dough should be very crumbly or shaggy and not seem like it will come together.

5. Turn the crumbs onto a work surface and gently knead. The heat of your hands will melt the butter just enough to bring the dough together. By hand, roll the loose ball into a disk about 1 to 2 cm (½ to ¾ inch) thick. Use a round butter of the desired size to cut out the biscuits. The unbaked biscuits may be frozen and cooked without thawing; just add 10 to 15 minutes to the baking time.

6. Place the biscuits on a parchment-lined baking sheet. Brush with beaten egg and sprinkle with a little salt. (If planning to split the biscuits to make open-faced sandwiches, turn and sprinkle the other sides with salt, too.) Bake until golden brown, about 35 minutes.