Preheat oven to 400 degrees. Grease a 8x8 or 9x9 baking pan.
Cook onion in first Tbsp. butter until tender. Set aside.
Mix Bisquick, milk and egg until just moistened. Stir in onions and 1/2 cup of the cheese and the parsley. Spread in greased pan. Dot with the 2 Tbsp. butter and sprinkle with the remaining 1/2 cup of cheese.
Bake 20 minutes or until toothpick in center comes out clean. Best served warm with lots of butter.