Sauté onions (I) in garlic butter. Place in a suitable bowl with the meat. Add bread crumbs, mustard and tomato ketchup and season with chili seasoning, salt and pepper. Shape burgers and place in refrigerator for 1 hour.
Cook baguettes with burgers and onions (Ii) on broiler until cooked. Cut the baguettes into slices. Put the potatoes on the grill as well.
Arrange the lettuce on the plates. Mix vinegar and oil and pour over salad.
Arrange the hamburger on the lettuce, spread the grilled onions evenly on top and arrange the potatoes and baguette slices on top.