Slice the flank steak thinly against the grain. In a bowl, whisk together the 1 tablespoon of oyster sauce, 1 tablespoon corn starch, 1 tablespoon water and 1/4 teaspoon baking soda. Add the cut meat and toss to fully coat, set aside.
Whisk together the ingredients for the sauce, set aside.
Heat a large skillet over medium high heat. Add 1 tablespoon canola oil (or oil of choice). Once oil is hot, add the steak. Cook until beef is browned on the bottom, then flip over. Continue cooking until beef is browned for another 1-2 minutes.
Add broccoli and sauce to pan, stir to coat everything and cover. Reduce heat to low. Let cook for a couple more minutes.
Remove from heat, stir again to coat in sauce and serve.