Season the chicken thighs with salt and pepper. This builds the base of flavor for the dish.
Set the Instant Pot to sauté. Add the olive oil and brown the chicken thighs on both sides until golden. You’re not cooking them through yet—just developing color and flavor. Remove and set aside.
In the same pot, add the onion and bell pepper. Sauté until they start to soften, about 3 to 4 minutes. Add the mushrooms and cook for another 2 minutes to release their moisture.
Stir in garlic and cook for about 30 seconds until fragrant. Add tomato paste and stir to coat the vegetables, letting it toast for a minute.
Pour in the white wine (or extra broth) to deglaze the pot, scraping up any browned bits from the bottom. Let it simmer for 1 minute to reduce slightly.
Return the chicken to the pot along with crushed tomatoes, broth, oregano, basil, and red pepper flakes. Stir to combine. Add olives if using.
Seal the Instant Pot and cook on high pressure for 8 minutes. When the timer beeps, allow a natural release for 10 minutes, then finish with a quick release.
Open the lid and check that the chicken is cooked through and tender. If you want a thicker sauce, you can simmer on sauté for a few minutes until it reaches your preferred consistency.
Taste and adjust seasoning with salt and pepper. Stir in fresh parsley for brightness just before serving.
Serve hot over spaghetti, tucked into crusty bread, or with a side of polenta or mashed potatoes to soak up all that delicious sauce.