Spinach Cheese Squares

2 tablespoons butter (homemade from local cream, Whitehall)
4 eggs (Boule Farm, Whitehall, or Stewart’s)
1 cup flour (Champlain Valley Milling, Westport)
1 cup milk (I always buy Stewart’s milk)
1 tsp. salt
1 tsp. baking powder
Pinch nutmeg
1 medium onion, well-minced (from my garden)
Fresh spinach (from my garden)
1 lb. Monterey Jack or any [...]