In a skillet, fry the bacon until lightly golden and remove. Sweat the onions down in the bacon grease. Turn up the heat and crumble brown the ground beef. Remove the beef (with a slotted spoon) from the pan, then discard the excess grease. Mix the beef, garlic, paprika, cayenne pepper and salt and black pepper to taste in the skillet.
Peel the potatoes. In a bowl, whip the eggs, milk, nutmeg and salt and pepper to taste. Carve the potatoes into 1/4 inch slices. Grease the sides of a 5x9 inch pyrex bread pan with butter. Layer 1/2 of the potatoes on the bottom of the pan. Add salt and pepper to taste. Scatter 1/2 of the bacon over the potatoes. Layer all of the beef mixture over the potatoes and bacon. Scatter the remainder of the bacon over the beef mixture. Layer the top with the rest of the potatoes. Add salt and pepper to taste. Pour the milk/egg mixture over the potatoes. Shake the pan to distribute the liquids evenly.
Bake the Musaka - uncovered - until the potatoes are tender and the top well-browned - about 50 minutes. Allow the dish to rest for 15 minutes at room temperature. To serve, carve it into thick slices.