In a medium pot, heat 1 tablespoon butter over medium high heat. Sear the goose legs until golden brown on all sides. Add bay leaf, one juniper berry, port wine and ½ cup of the game stock. Cover and let simmer for 45 minutes before reducing the liquid by removing the lid and simmer for about 10 minutes more.
In another medium pot, put the rest of the game stock to a boil. Add fennel and broccoli and boil until tender. Drain, return pot to heat to steam away excess liquid. Transfer to blender; add 1one or 2 tablespoons butter and puree. Return to pot and add salt, pepper and nutmeg to taste. Keep warm.
In a third medium pot, bring water to a boil. Add Brussels sprouts and boil for 3 minutes. Strain and stop the boiling process by plunging them into cold water, leaving the tap running. Pat dry and set aside until further use.
Cut a shallow square pattern in the fat layer of each goose breast. In a small bowl, combine 1 juniper berry, cinnamon and coriander. Rub meat with spice mixture. In a skillet, heat 1 tablespoon butter over medium high heat. Sear the breasts on both sides. Lower the heat and continue to cook until medium rare (or core temperature is 135°F [57°C]).