Add onions to the heated oil and cook for 1 minute.
Stir in garlic and ginger and cook for 30 seconds, stirring.
Season beef with fresh ground pepper and add to the Instant Pot; cook until just browned on both sides.
Stir in the prepared stir fry sauce.
Lock the lid and select HIGH PRESSURE; set cook time for 12 minutes.
When cook time ends, use Quick Pressure Release and when the valve drops, remove the lid.
Set Instant Pot to the Keep Warm setting.
Add broccoli florets to the Instant Pot and close with the lid; let broccoli steam for 5 to 6 minutes, or until cooked to a desired tenderness.
In a small mixing bowl whisk together water and xanthan gum.
Pour xanthan gum mixture into the liquid inside the Instant Pot; stir until completely combined and until sauce has thickened.
Garnish with sesame seeds, scallions, and red pepper flakes; serve.
Notes
HOW TO STORE BEEF & BROCCOLI LEFTOVERS Store leftovers in an airtight container and keep in the fridge 3 to 4 days. Reheat over medium-heat on the stovetop. You can also reheat it in the microwave.