At least a half an hour before cooking, combine ingredients for marinade in a resealable bag, add steak and let marinate for at least 30 minutes.
Allow steak to sit at room temperature at least 30 minutes before grilling.
Begin preparing vegetable portion of sandwich. Once chopped and julienned, add into a bowl for mixing.
In a small pan, add 2 tablespoons of vegetable oil, heating to medium. Once heated add the portion of the vegetables to be sauteed (garlic, ginger, jalapeno,s and shallot). Saute for about 5 minutes until lightly browned. Allow to cool and toss with the rest of your vegetables.
Add ingredients for vegetable sauce into a small bowl, whisking until combined, and toss vegetables with it.
Drain about a tablespoon of the leftover vegetable sauce from the vegetables, along with a tablespoon of leftover marinade, and a tablespoon of sesame oil, and toss the bok choy in it.
Heat barbecue to medium-high heat.
While barbecue is pre-heating prepare steak sauce. Combine hoisin, sriracha, sesame seeds and hot water in a bowl, mixing until smooth.
Once barbecue is heated, cook steak for about 3-4 minutes on each side for medium-rare, brush with steak sauce while cooking.
Grill bok choy for about 4 minute, until lightly charred.
Butter bread and toast on barbecue as well.
Once steak is done, let it rest 5-10 minutes.
Spread a layer of mayonnaise on the bottom slice of bread. Top with bok choy, and a little bit of the vegetable mix.
Thinly slice steak, place on sandwich, drizzle with some leftover steak sauce, top with more mixed vegetables, and form sandwich!