STEAK
Mix marinade ingredients together and pour over the flank steak. Place in a zip lock overnight to marinade.
Take steak out of the marinade. Place your largest sauté pan over medium heat. Once the pan is hot, add 1 tablespoon oil and wait until shimmering. Place flank steak in the hot pan and shake for a few seconds to prevent sticking. Turn heat to medium and brown on each side for about 4 minutes. Transfer to a sheet tray or baking dish.
Finish in the oven at 400°F for about 10 minutes or until the steak reaches medium-rare to medium, an internal temperature about 130°F to 135°F. Let rest before slicing against the grain.
While the steak is cooking, assemble your stir fry.
NOODLES
In a medium size pot boil water and blanch the bok choy for about 2 minutes. Take out bok choy and place in ice water to keep green while you prepare the rest of your dinner.
Empty the pot and return to the stove with the beef stock. Bring to a boil. Dunk the noodles in the pot and bring back to a boil and take out the noodles with tongs. Place noodles in a bowl.
Mix together the soy, peanut butter and chili garlic oil. Add to the remaining beef stock pot and whisk until combined
Ladle the sauce into 4 bowls. Divide the noodles between the 4 bowls. Add the bok choy, sliced flank steak and tear up some cilantro to garnish. I like to finishwith a bit more chili garlic sauce. Serve.