Heat olive oil in a skillet over high heat. Add livers and sautÚ until tender and brown. Add garlic when livers are almost ready.
Season with salt and pepper. Add balsamic vinegar. Remove livers from skillet and reserve. Boil cooking liquid for 2 or 3 minutes more.
Mix all ingredients. Serve warm.
Combine lettuce, ar˙gula leaves, chicken livers, dressing and warm cooking liquid just before serving.