Preheat oven to 120°C/250°F. Make incisions at the joint-end of the goose legs. Season with salt, then set aside. Peel and dice celery root. Peel carrots and cut into bite-sized pieces. Cut leek into 1.5-cm/ 0.5-in. slices. Peel and roughly chop onions. Cut a part of the apples into bite-sized pieces.
In a roasting pan, heat clarified butter. Transfer goose legs to the roasting pan and sear on medium-high heat. Remove goose legs and transfer vegetables and apples to the roasting pan. Add tomato paste and stir to combine. Deglaze with red wine and reduce to half. Add goose stock, bay leaves, a part of the cinnamon, and thyme and stir to combine. Season to taste with salt and pepper.
Transfer roasting pan with vegetables to the oven at 120°C/250°F. Place goose legs on an oven rack above and bake for approx. 2.5 hrs.
Heat a part of the butter in a large pot. Add vegetable stock and milk. Finely grate nutmeg. Season to taste with salt and pepper. Bring to a boil and add polenta. Reduce heat and let simmer for approx. 5 min., stirring often. Transfer polenta to a baking dish lined with plastic wrap. Smooth down, cover polenta with plastic wrap, and refrigerate.
Slice off the bottoms of the remaining apples and hollow out, using an apple corer. Heat remaining butter in a large pot. Add sugar and remaining cinnamon. Stir almond slices into the butter-sugar mixture and let toast for approx. 2 min, or until golden brown. Add raisins, orange juice, dark rum, and lemon juice, and stir to combine.
Place apples on a baking dish and stuff with almond-raisin mixture. Transfer to the oven at 120°C/250°F for approx. 30 min.
Remove polenta from the fridge. Cut off the edges, then cut polenta into 3x4-cm/ 1x1.5-in. pieces. Heat oil in a frying pan and fry polenta for approx. 2 min., or until golden brown on both sides.
Remove roasting pan with vegetables from the oven, place a baking sheet under the oven rack and raise temperature to 220°C/425°F. Return tops to baked apples and bake for another 15 min. Using a sieve, strain sauce from vegetables into a pot. Bring to a boil and let simmer for approx. 10 min. Mix cornstarch and water in a small bowl to make a slurry. Add slurry to the sauce and stir to combine.
Remove goose legs and stuffed apples from the oven.
Serve stuffed apples, polenta, and goose leg and pour the sauce over the goose legs. Enjoy!