Preheat oven to 400°F. Grease 12 muffin cups. In a large bowl mix together all dry ingredients. In a separate bowl, whisk together yogurt, butter and eggs. Stir into flour mixture just until combined. (Do not over mix or muffins will be tough) batter will be very thick.
Spoon into prepared muffin cups.
Bake in preheated oven for 18- 20 minutes, or until golden. Remove from oven. Run a knife around edges of muffins. Cool for at least 5 minutes in the pan before removing.