Preheat oven to 350 degrees. Arrange fennel in a 10 inch baking dish, and scatter butter and garlic around fennel. Season to taste with salt and pepper. Add hot stock and bake until tender and browned, about 1 1/2 hours. Preheat broiler. Spoon cream over fennel, sprinkle nutmeg over cream, then sprinkle fennel with parmigiano-reggiano. Broil until golden, about 1 minute.