Set your Instant Pot to sauté. Add a little oil and cook garlic, ginger, and onion for about 2 minutes until onions look soft and smell amazing.
Add chicken pieces and red curry paste. Stir to coat chicken evenly with the paste.
Pour in coconut milk and chicken broth. Add mushrooms, bell pepper, and fish sauce. Stir gently so nothing sticks to the bottom.
Seal the Instant Pot lid and cook on high pressure for 10 minutes. Quick-release carefully when done.
Add lime juice, taste, and adjust seasoning with extra fish sauce or salt if needed.
Ladle into bowls and garnish with fresh cilantro. Optionally, sprinkle chili flakes for extra heat.