Set the Instant-Pot to saute then set it on normal-heat. When the oil is hot, add the onion, garlic, scallions, jalapeno and ginger, . Sauté for a few more minutes, or till the vegetables become limp.
Add the chopped-chicken pieces and stir. Stir in the red-pepper-flakes. Continue to saute for about 30 seconds. Add the chopped-mushrooms. Continue to saute the chicken till it changes color completely and the vegetables are soft. It should take for 3-4 minutes.
The vegetables and chicken will now release natural-juices. This is what need to build pressure in our Instant-Pot. 1/3 cup water can be added if the mixture feels dry.
Cancel the saute feature. De-glaze the pot by scraping the sides and bottom with a spatula. Seal the Instant Pot's lid. There is no need to add any liquid.
Pressure cook on high for only 1 minute. The Instant-Pot will start to beep after the pressure cooking cycle has ended. Perform a quick pressure release manually by moving valve from sealing to venting position.
Carefully open the lid. The result will be perfectly cooked chicken with some liquid. Add all the sauce ingredients and mix everything together. Cancel the pressure cook function and turn the Instant-Pot to saute. Turn it up to high heat.
Let the sauce simmer till it thickens for 5-6 minutes. The sauce should adhere to the chicken, but not drip from the spoon. The chicken should be moist, but not soggy with runny sauce.
Add the sesame-oil to the mixture and mix well. Now you have a super moist and oily chicken that can be served on lettuce leaves.
Rinse the lettuce leaves thoroughly. Drain any excess water. Each leaf of lettuce should be placed on a separate plate. Place enough chicken on top of each leaf.