If making rice or noodles to serve with this stir fry, get that started. Prep all stir fry ingredients ahead of time as the actual cooking part goes very quickly. To prep the steak, trim off any fat and slice it across the grain into very thin bite-size pieces. Add the sauce ingredients to a bowl and whisk together thoroughly.

Add one tablespoon of the olive oil to a large skillet over high heat. Let the pan heat up for a few minutes (oil should be shimmering).

Add the onion, broccoli, and bell pepper and cook for 4-5 minutes, tossing/stirring often (they will end up tender-crisp). Transfer veggies to a plate.

Add the other tablespoon of olive oil to the skillet. Add the beef in a single layer (just "sprinkle" it into the pan ensuring it's spread out a bit) and don't touch it for a minute. Stir/flip it (cooking tongs are helpful) and cook it for another minute or so. Important: it cooks fast and will easily overcook and become tough. Leaving it a bit rare at this point is best.

Add the veggies back to the skillet and pour the sauce in. Stir/toss until coated and the sauce has thickened (about 1-3 minutes). Take the skillet off the heat and serve immediately over rice or noodles.