For the garlic chicken USA, clean the chicken and remove and keep the liver.
Mix the balsamic vinegar, 2/3 of the oil, mustard, salt and pepper to make a marinade, then add the cornflour and 2 cloves of garlic. Mix again thoroughly. Now generously coat the chicken both inside and out with the marinade and let it marinate for 5 hours in the refrigerator.
In a small frying pan, heat the butter with the sage leaves over medium heat until completely melted and brown. Sauté the chicken livers in it for 1 minute on each side. Season with salt and pepper and add a slice of bread. The liver can now be eaten as an appetizer.
Place the remaining garlic cloves whole, but without their skins, in a greased oven dish in the oven at 180°C. Cut leeks into rings and place in the oven with the marinated chicken along with the garlic.
Let the garlic chicken USA sizzle in the oven for about 45 minutes.