Preheat oven to 375 degrees. Lightly butter or spray a 9x13 pan.
In a medium bowl, combine flour, salt, and sugar. Cut in butter with a pastry cutter or fork till about the size of small peas. Add 1 cup of the buttermilk, mixing lightly with a fork until combined. Add more buttermilk, 1 tablespoon at a time, just until all the flour is mixed in. Turn out onto lightly floured board and knead gently for about 5 minutes, mixing in a little flour while kneading so the dough isn't sticky. Roll dough out to about 1 inch thickness. Cut with a 3 inch biscuit cutter or glass dipped in flour(a smaller cutter can be used and will yield more biscuits). Place in pan about 1 inch apart. Brush with melted butter, if desired (this helps to make the tops golden). Bake for about 20-25 minutes until golden and done. Remove from oven and brush with melted butter again, if desired.