Toss the sliced beef with baking soda in a bowl and let it rest for 10 minutes to help tenderize the meat.
Rinse the beef thoroughly with cold water to remove the baking soda, then pat dry and season lightly with salt and pepper.
Warm the olive oil in a large skillet or wok over medium-high heat.
Add the beef in batches if needed, cooking 2–3 minutes per side until browned and cooked through, then transfer to a plate.
In the same pan, add the broccoli and a splash of water to the skillet, cover, and steam for 2–3 minutes until just fork-tender.
Return the beef to the pan and toss to combine.
In a small bowl, whisk together all the sauce ingredients until the mixture is smooth and lump-free.
Pour the sauce into the skillet and cook, stirring often, for 2-4 minutes or until it thickens and coats the beef and broccoli.
Remove from heat and garnish with sesame seeds before serving.