sprinkle with salt and pepper. Broil in oven directly on rack 6-8 minutes over a pan or tinfoil to catch juices, and then set aside.
Heat 1/2 cup water and the butter. Steam spinach 2-3 minutes until wilted. Drain thoroughly and chop. In a sauté pan over medium high heat, sauté the garlic in the olive oil until barely golden. Add spinach and cook 1-2 more minutes before adding cream and oysters. Mix carefully, reduce heat and simmer 5-6 minutes.
Mix 3 tbsp of the parmesan cheese, the bread crumbs, fennel seed and nutmeg. Stir gently into oyster/ spinach mixture. When well mixed fill the mushrooms with the oyster Florentine, and top with the remaining parmesan cheese. Place in a greased pan and bake at 350 degrees for 6-8 minutes. Garnish with chopped chives and serve.