Preheat the oven to 425°., Place the flour in a bowl. Work in the butter or shortening just until crumbs are the size of large peas., Add 2/3 cup of the milk or buttermilk, and stir until the mixture holds together and leaves the sides of the bowl, adding more milk or buttermilk if needed., Scoop the dough onto a well-floured surface, and fold it over on itself several times, using more flour as needed to prevent sticking., Roll or pat the dough into a 5" x 8 1/2" rectangle about 1/2" to 3/4" thick., Cut biscuits with a sharp, round 2" cutter, dipping the cutter into flour between cuts to reduce sticking. Or cut the rectangle into 12 small rectangular biscuits, which will allow you to skip the step of re-rolling and cutting scraps., If you've used a round cutter, pat the scraps together, and cut additional biscuits., Place the biscuits on an ungreased baking sheet, leaving about 1" between them for crisp biscuits. Arrange biscuits so they're barely touching for soft-side biscuits. For higher-rising soft-side biscuits, place biscuits in an 8" round pan., Bake the biscuits for 10 to 14 minutes, or until they're a light golden brown., Remove them from the oven, and serve hot. Cool leftovers completely, wrap airtight, and store at room temperature for several days; freeze for longer storage. To refresh room-temperature biscuits, place on a baking sheet, tent lightly with foil, and bake in a preheated 350°F oven for 10 to 13 minutes, until heated through.