Melt butter in the bottom of the Instant Pot with the Saute feature. Add the chicken thighs and brown for 1-2 minutes per side.
Turn off the Saute feature and add the onions to the pot. Whisk together the sriracha, soy sauce, vinegar, honey, garlic and ginger in a medium bowl. Pour the sauce into the Instant Pot. Seal the lid and select manual high pressure for 12 minutes.
Once the chicken thighs have finished cooking, allow for a natural release for 5 minutes and then turn the steam valve to quickly release any remaining steam.
Remove the chicken thighs to rest on a plate. Turn the Saute feature back on and simmer the remaining liquid to reduce to a sauce, stirring occasionally. Once the sauce has thickened, return the chicken thighs to toss and coat in the sauce. Sprinkle with sesame seeds and garnish with fresh cilantro. Serve immediately.
Cooked in a 6 quart Instant Pot Duo.
Frozen chicken thighs can be used, increase the cook time to 16 minutes.
Leftovers will keep well for up to 4 days in the fridge and can be reheated in the oven.
If you like things spicier, you can season the thighs with a little cayenne as well as paprika.