Sauté the onions and mushrooms in butter and lemon juice until softened. In a separate bowl, beat the eggs and yolks then add the cream and other seasonings until well blended. Add the mushrooms, onions and most of the cheese. Pour into the quiche shell and bake at 350 degrees F for 35-40 minutes on the center oven rack. Check by poking a knife into the middle - if it's clean, it's done. Remove and let cool. Garnish with paprika or cheese.