Preheat the oven to 375 degrees F. Lightly grease a 6 cup oval ceramic ramekin. In a large saute pan, melt the remaining butter. Add the onions and season with salt and pepper. Saute for about 2 minutes, or until the onions are soft. Add the spinach. Season with salt and pepper. Saute for 3 to 4 minutes. Add the garlic and cream. Mix well. Season the mixture with salt and pepper. Bring the liquid to a boil and reduce to a simmer. Simmer the mixture for 6 minutes. Remove the pan from the heat and turn into the prepared pan. Sprinkle the top with the grated cheese and place in the oven. Bake for about 4 to 6 minutes or until the cheese is slightly brown and bubbly.