Slice the vegetables and blend the mustard soy sauce ingredients until the sesame seeds are pulverized into small pieces. Set both aside.
Heat your Bull Griddle: Preheat your griddle to medium-high heat. Once hot, drizzle with the avocado oil.
Pat the steaks dry with a paper towel and season generously with salt and pepper. Sear the steaks for 2-3 minutes per side for a nice sear and medium-rare doneness. Alternatively, use a meat thermometer to cook to your desired temperature (145°F for medium-rare). Remove the steaks from the Bull Griddle and tent with foil to let them rest.
Cook the vegetables: Add the sliced vegetables to the hot griddle and cook for 3-5 minutes, stirring occasionally, until tender-crisp.
Deglaze the Bull Griddle (optional): For extra flavor, add a splash of water or broth to the Bull Griddle and scrape up any browned bits. This deglazed liquid can be incorporated into your mustard soy sauce for extra oomph. If you're cooking fried rice this is a great time to cook it.
Slice the rested steaks against the grain and arrange on a plate with the cooked vegetables and, if desired, fried rice. Drizzle generously with the prepared mustard soy sauce and garnish with sesame seeds.