Trim, wash and dry the spinach thoroughly and place in a salad bowl.
Coat a saute pan with 2 tablespoons olive oil and put over medium heat. Fry the prosciutto and garlic for a minute to flavor the oil, then add the mushrooms and onions. Saute mushrooms and onions until they are slightly brown and tender, about 3 minutes.
Scrape the mixture on top of the spinach, return the pan to the stove.
Add balsamic vinegar and scrape up the bits at the bottom of the pan. Add remaining oil and honey. Swirl pan around for a minute to warm the vinaigrette.
Pour the vinaigrette over the salad and top off with Gorgonzola. Season with salt and pepper, toss and serve.