Bring a large pot of water to a boil. Add the cabbage head and cook, lifting the cabbage out of the water occasionally to peel off and drain the large outer leaves as they loosen. Trim off any tough ribs. In a large skillet, melt 1 tablespoon of the butter over medium heat, then add the garlic and leek. Cook, stirring occasionally, until the leek is soft, about 10 minutes. Turn the mixture into a bowl and mix in the eggs, salt, pepper, and nutmeg. Add half of the mixture to the mashed potatoes and mix well. Add the remaining half of the mixture to the mashed carrots and blend well. Line the bottom and sides of the prepared casserole with cabbage leaves, using 4 to 8 leaves. Reserve 4 to 8 whole cabbage leaves to cover the top of the pie. Finely chop and drain the remaining cabbage. Sprinkle the bottom of the casserole with l/2 of the ham cubes; cover with the potato mixture and then a layer of chopped cabbage. Top with the carrot mixture and the remaining ham. Top with the reserved cabbage leaves. Dot with the remaining 2 tablespoons butter. Bake the pie for \1A hours or until it feels firm in the center when pressed lightly. Serve hot with melted butter (if used).