Preheat the oven to 375 degrees F. Place the lamb, onion and garlic in a pot and cook the meat through over medium heat. Drain the excess fat. Add the next five ingredients. Bring to a gentle simmer and cook 10 minutes; remove from the heat. Peel the potatoes, very thinly slice, place in a bowl and cover with cold water.
Whisk the milk and flour together in a pot. Set over medium heat and bring to a simmer. Cook, stirring, until the sauce thickens; remove from heat. Beat the eggs in bowl until somewhat lightened and frothy. Very, very, slowly whisk in the hot white sauce. Mix in the feta and paprika; season with salt and pepper.
Lightly olive oil a 9 x 13-inch baking dish. Drain the potatoes; layer half in the bottom of the dish. Pour half the egg mixture over the potatoes. Top with the lamb mixture, and then arrange remaining potatoes on it. Cover with remaining egg mixture. Bake 60-70 minutes, or until the potatoes are tender when checked with the tip of a knife. Rest the moussaka 10 minutes before cutting into portions.