Preheat the oven to 190ºC degrees. Butter a large casserole dish and set aside. Combine the butter, milk and the cream in a heavy saucepan and heat nearly to the boil. Stir i the grits and cook for 20-25 minutes, stirring as necessary to prevent scorching. A non-stick pan is handy for this task. Remove from the heat and stir in the spinach, green onions, and the grated cheddar cheese. Stir in the eggs whisked with the milk. Season to taste with salt and pepper. Pour into the prepared casserole dish and sprinkle with the parmesan cheese. Bake for 30 minutes or until the top is golden. serve at once.