Slice your steak into 1/6-1/8 inch slices, against the grain, on a bias (see the recipe notes below for a trick to create the best thin slices).
Grate the ginger and garlic, and mix them together with all the marinade ingredients in a medium bowl. Add the slices of beef. Marinate in the fridge for about 20 minutes (OR leave in the fridge overnight for even more flavour).
Heat a large skillet or wok over medium-high heat and add 1 tablespoon of the olive oil and 1 teaspoon of the sesame oil. When the oil is hot, add in the beef so the bottom of the pan is covered but not overcrowded. You may have to cook the beef slices in 2 batches.
Flip the beef slices once they start to brown and caramelize - this should take only a minute or two since the slices are thin.
When the beef is browned on both sides, remove it to a plate repeat with the remaining beef slices.
Once all the beef is cooked, wipe the wok with a kitchen paper towel.
Measure out the rice vinegar, soy sauce, hoisin sauce, brown sugar and sriracha(if using), mix them and set aside. Mix the water and cornstarch in a separate small bowl to create a slurry to thicken the sauce.
Add 1 tablespoon of olive oil and 1 teaspoon of sesame oil to the skillet or wok. Add the garlic and ginger and fry until fragrant.
Add the broccoli florets to the skillet and sauté for just a few moments.
Add the beef stock and let it bubble under a lid until the broccoli becomes vivd green. Remove the broccoli to the plate with the beef.
Add the sauce ingredients to the pan and mix them well, until the brown sugar dissolves. Add in the cornstarch mixture and cook until the sauce becomes transparent and thickens.
Add the beef and broccoli (with the juices on the plate) back in and toss everything together with the sesame seeds.
Serve over rice.