Preheat oven to 425 degrees F (220 degrees C). Whisk together the first five ingredients in a bowl. With your fingers, two forks or a pastry cutter, cut in the butter until mixture forms pea-sized crumbles. Mix in cheese and thyme. Gently mix in buttermilk until loose dough forms, and then turn on to a floured surface. Shape into a ball, and then flatten into a 3/4-inch thick disc. Cut into 2-inch rounds and place on a non-stick or parchment-lined baking sheet. Bake in the middle of the oven 12-15 minutes, until puffed and golden. Turn to broil for 1 minute to brown the tops, if desired.