Combine all dry ingredients well by stirring together in a large mixing bowl.
Grate frozen butter through the large holes of a box grater directly into the dry ingredients. Add cheese and green onions and and toss until all are coated.
Stir in buttermilk gently just until all ingredients are incorporated. To keep the biscuits light, handle as little as possible. The dough will be a rather shaggy mass – you don’t want it to be smooth.
Scoop dough, by scant half cups, onto parchment or wax-paper covered baking sheet and freeze. When frozen, transfer to zip-lock bag. (Biscuits keep well this way for up to a month).
To bake: Heat oven to 425. Take biscuits from freezer and let sit out just while oven heats. Place on parchment covered baking sheet, brush tops of biscuits with milk or melted butter and bake on center rack of oven until golden – about 15 – 20 minutes.
To make Sweet Potato variation –
Add a teaspoon of sugar and a tablespoon of crumbled sage to the dry
Substitute a 1-1/4 cups mashed sweet potatoes for the cheese and green onions
Mix sweet potatoes with buttermilk before incorporating