Chop chicken breasts into 1"- 2" chunks and roughly chop the onion.
Add the sesame oil to the Instant Pot and choose "saute."
Mix salt, black pepper, curry, ginger, and crushed red pepper until combined and stir with chopped chicken and onions.
Add the chicken and onions to the Instant pot and set a timer for 5 minutes.
Sauté the spiced chicken and onion mixture until the chicken is browned for approximately 5 minutes. Add chopped garlic during the last minute. Make sure to scrape the bottom of the pot, to avoid "burn" error.
Mix stewed tomatoes, tomato paste, and chicken broth in the same bowl the chicken was in. Stir the mixture in with the chicken and onions.
Cover with the lid and lock it into place. Set the valve to the "seal" position, choose "high pressure," and set the time to 20 minutes. When the time is up, "quick release" the pressure.
Unlock the lid and mix in the peanut butter.
Lock the lid once more and move the lever to "seal." Cook on high pressure for another 10 minutes, followed by a "quick release."
Serve stew in deep bowls, topped with a tablespoon of roasted peanuts, and chopped fresh cilantro (optional).