Combine all of the sauce ingredients in a small bowl. Whisk until no large lumps of cornstarch remain. Set aside.
Pat the steak dry with a paper towel. Very lightly season it with salt and pepper on both sides.
Add the olive oil to a heavy bottomed skillet (like stainless steel or cast iron) set over medium-high heat. When the olive oil is hot, add in the steak and sear for 2 minutes per side.
Remove the steak to a plate. Add the remaining stir-fry ingredients (snow peas, broccoli, carrot, and green onion). Cook, stirring occasionally, until the vegetables are crisp tender -- about 3-4 minutes over medium-high heat.
While the vegetables are cooking, thinly slice the steak against the grain in about ¼” slices.
When the vegetables have finished cooking, reduce the heat to medium. Give the sauce ingredients another good stir and add it to the pan. Stir until it starts to thicken, 1 to 2 minutes.
Once the sauce has thickened enough to coat the back of a spoon, add the sliced steak and toss to combine.
Serve immediately, garnished with sesame seeds and a squeeze of fresh lime juice, if using.
Substitute chicken, shrimp or tofu for the beef, if desired.
Add or substitute different vegetables, such as mushrooms, onions, celery, bell peppers, zucchini, or whatever you like.
Like a lot of spice? Add more ginger, or more Sriracha, or red pepper flakes.