Heat a large saute pan over medium-high heat. Add 1 tablespoon oil and allow to heat up. Add onion, garlic, mushrooms, and carrot, saute for 2 minutes. Add scallion and saute 1 minute. Add tofu and cook 1 minute to warm (do not discard sauce). Turn heat to low and add noodles, spinach, sesame oil and sauce. Gently stir to combine until noodles are coated with the sauce. Serve topped with sesame seeds.