Turn your Instant Pot to "Saute", then add vegetable oil to the pot. Add the meat and cook until browned, breaking up the meat with a spatula as it cooks.
Add the onion, bell pepper, and poblano peppers and cook for 4 more minutes, or until softened. Scrape the bottom of the pot with a wooden spoon as the onions and peppers cook and give off liquid.
Add garlic and cook, until fragrant, about 30 seconds. Drain grease if needed, and return meat mixture to the pot.
Add all remaining ingredients and stir, scraping the bottom of the pot to ensure no browned bits remain.
Cancel the saute function, and secure Instant Pot lid, making sure the valve is set to "sealing". Press the Pressure Cook or Manual button and use the +/- buttons to set the timer for 15 minutes.
Once the timer beeps, let out the pressure by carefully moving the valve to “venting" to perform a quick release. When the pin drops, remove lid and set aside.
If you prefer a thicker chili, mix 2 Tbsp cornstarch with 2 Tbsp water in a small bowl until smooth. Stir into the chili and press the "saute" button again. Cook, stirring often, for several minutes, or until thickened to your liking.
Serve hot, with desired toppings.