Preheat the oven to 425 degrees F. Sift the flour then measure it to yield 2 cups. Sift it again with the baking soda and salt into a mixing bowl. Add the shortening and using a pastry cutter or fork, work the shortening into the flour to form a crumbly dough. Make a well in the center of the dough and pour in most of the buttermilk (reserve a couple of tablespoons). Stir the mixture to form a soft dough. If needed, add the remaining buttermilk to form a soft dough. Place the biscuit dough on a lightly floured work surface. Sprinkle the top of the dough lightly with flour. Knead the dough 5 or 6 times, no more. Pat the dough out into a 1/2-inch thick round. Cut the dough with round biscuit cutters and place on an ungreased baking sheet. Place the biscuits in the oven and bake at 425 degrees F for 12-15 minutes or until lightly browned. Remove from the oven and let cool on a wire rack. cook's notes If you do not have buttermilk, you can make sour milk by adding 4 tablespoons vinegar to 3/4 cup of milk.