Add the cleaned and thinly sliced mushrooms to the pan. While the mushrooms are sautéing, add 1 tablespoon of balsamic vinegar. The balsamic vinegar will combine with the caramelized onions to balance the acidity of the dish and elevate the hidden umami character of the mushrooms. Sauté for approximately
10 minutes until the mushrooms release their water and it evaporates.