Place all the ingredients in the Instant Pot (except for the broccoli if you want it to stay firm, the cornstarch slurry, and the sesame seeds). Start with the sauce ingredients, then add the shrimp. Cover with the lid, ensuring the vent is in the SEALING position.
Press "manual" or "pressure cook," set to low pressure, and cook for 0 minutes. Let the Instant Pot come to pressure. Once it beeps, quickly release the steam and carefully open the lid.
To thicken the sauce, press "saute" and add the cornstarch slurry to the pot, mixing it with the sauce. The sauce will thicken in about 1 minute. If it's not thick enough, add another cornstarch and water mixture. Mix in the sriracha sauce if using.
After thickening the sauce, add fresh broccoli florets to the pot and cover with the lid. Allow the broccoli to "steam" for a couple of minutes until it's slightly cooked but still firm and crunchy.
Serve over rice and garnish with sesame seeds.