Mix together all the ingredients for the marinade in a bowl.
Pour marinade over beef slices, toss until beef is evenly coated. Be gentle as you don't want to tear the slices. Let beef marinade in the fridge for 15-30 minutes.
Meanwhile, cut the roots off of the enoki mushrooms. Then, break into smaller bunches.
On a clean bench or large plate, spread out one slice of beef and place enoki mushrooms on one end. Roll up tightly. Repeat for the remaining beef and enoki mushrooms.
Heat up a nonstick skillet over medium heat. Add enoki beef rolls and cook for 1 minute. Keep rotating and searing until beef is browned on all sides.
Transfer enoki beef rolls to serving plate and garnish with sesame seeds and chopped spring onions if desired. Serve immediately.