In a mixing bowl, combine dry ingredients including flour, baking powder, baking soda, and salt.
Using the pastry cutter, cut in the diced butter, yogurt, and milk. Add up to ½ cup more milk if the dough is dry and crumbly. Fold in cheese and chopped onions.
Lightly flour a clean work surface. Spill contents of bowl and start to combine by squishing together. This will come together as one lightly sticky ball. With the dough ball, make a flat circle about ½ inch tall.
Use your biscuit cutter (must be a sharp cutter) and cut up to 8 large rounds. Brush with milk on top.
Cook for 10-12 minutes. Eat while warm. Save up to a week (good luck). Freeze up to a month.