Add olive oil to the inner pot and heat until hot on Sauté, Normal setting
Add onion and cook until lightly browned on Sauté, Normal setting (about 7 minutes)
Add garlic and continue to sauté 1 minute
Add chicken broth and deglaze with a wooden spoon (important to prevent Instant Pot "burn notice")
Layer evenly with chicken breasts
Layer evenly with cherry tomatoes
Drizzle with balsamic vinegar and add chili flakes
Add kosher salt and black pepper
Close and lock the lid and turn the steam release handle to Sealing
Pressure cook - High, 12 minutes
When done cooking, quick release pressure
Sprinkle with mozzarella and fresh basil
Close lid and let sit for 5 minutes to allow cheese to soften