In a 12 to 14-inch saute pan, heat olive oil until smoking. Add onion and garlic and saute until just softened, about 4 minutes. Add Mortadella and stir until lightly browned, about 2 to 3 minutes. Add frisee, thyme and balsamic vinegar and toss until just wilted, about 45 to 60 seconds. Season with salt and freshly ground pepper and divide among 4 plates. Shave Parmesan cheese over each salad using a vegetable peeler and serve warm.