Combine gin, port, thyme and juniper berries in a medium shallow baking dish. Add the venison and turn to coat. Cover and marinate in refrigerator for 30 minutes.
Heat oil in a large saute pan over high heat until almost smoking. Remove the venison from the marinade and shake off excess. Season with salt and pepper, to taste. Cook on 1 side until golden brown. Turn over, reduce heat to medium and continue cooking until medium-rare, 3 to 4 minutes. Serve with the sauce and Sweet Potato and Plaintain puree.
Heat butter in a medium saucepan over medium-high heat. Add the onions, celery, garlic, and carrots and cook until soft. Raise the heat to high and add the port, cook until dry. Add the port, cranberry juice, stock, cinnamon, allspice, and cranberries and cook until a sauce consistency is formed. Finish with the cold butter and season with salt and pepper, to taste.
Preheat oven to 375 degrees F.
Place potatoes and plantains on a large baking sheet and roast until the potatoes are soft, about 50 to 60 minutes and the plantains are completely black.
Slice each potato in half lengthwise, scoop out the flesh and place it in the bowl of a large food processor. Peel the plantains and add the flesh to the sweet potatoes. Add the butter, salt, cinnamon and 1/4 cup maple syrup and process until smooth. Add the cream and pulse until combined.
Place the puree into a medium baking dish and place in the oven for 10 minutes to heat through. Remove and drizzle the top with the remaining 2 tablespoons of maple syrup and serve.