Start by preparing the ingredients: chop the broccoli and bell peppers, mince the garlic and ginger, and measure out the other ingredients.
In the Instant Pot, combine 1 cup of water with the broccoli and bell peppers. Close the lid, set the valve to seal, and cook on high pressure for 2 minutes.
Once the cooking time is complete, do a quick release of the pressure. Open the lid and remove the vegetables, setting them aside.
In a mixing bowl, whisk together the soy sauce, rice vinegar, hoisin sauce, brown sugar, cornstarch, sesame oil, minced garlic, minced ginger, and red pepper flakes until well combined.
Pour the sauce mixture into the Instant Pot, and select the sauté function. Cook for about 2-3 minutes, stirring constantly until the sauce thickens.
Add the cooked broccoli and bell peppers back into the pot, tossing to coat them in the sauce. Simmer for 1-2 minutes to heat through.
Stir in the roasted peanuts just before serving.
Serve the Kung Pao Broccoli over cooked rice for a complete meal.