Peel raw potatoes and cut into thin slices. Halve leeks, clean, wash and cut into strips. Sautee in butter with chopped garlic. Add milk and cream to the leeks, bring mixture to a boil, add potatoes and season with salt, pepper and muscat. Keep stirring and let cook for 6 minutes. Butter casserole form, fill in potatoes about 2 cm high, cover with parmesan cheese and melted butter and bake in pre-heated oven at 180° Celsius for 20 minutes.