Preheat oven to 450 degrees F.
2 1/2 cups flour
2 teaspoons baking powder
2 teaspoons salt (can use considerably less)
1/4 teaspoon baking soda
1/2 cup butter or margarine (that's 1 stick. Don't use the kind of margarine that comes in a tub, it won't work. If you really really want to, you can use an equivalent amount of lard, which makes fabulous biscuits but is very bad for your health.)
1 cup buttermilk
Sift dry ingredients together. Add butter and blend well until like a fine cornmeal (I use a pastry cutter). Add milk and mix thoroughly (a well-seasoned wooden spoon works well). Roll dough out thin and cut into circles with a glass or jar mouth. Bake on greased pan until lightly browned. Serve with butter and jam, or honey, or syrup, or with fried eggs. Or anything, really.
To sour regular pasteurized milk as a substitute for buttermilk, add 1 tablespoon lemon juice or white vinegar to 1 cup milk and let stand at room temperature for 10-15 minutes before use.