Put the Instant Pot into saute mode and add the canola oil.
Sear the chicken for 4-5 minutes on each side until lightly browned. Then remove from the pot and set aside.
Next, add in the onions and cook for about 5 minutes until tender, scraping the brown bits at the bottom as you go.
Next, add in the garlic and cook for about 1 minute.
Add the tomato sauce, chipotle peppers, and chicken stock and allow to reach a boil.
Blend the sauce using an immersion blender (or traditional blender), then add the chicken back into the sauce.
Cook at high pressure for 20 minutes. You can use natural or manual release of the pressure once done.
Once it has cooled slightly, shred the meat using a fork. Serve immediately or refrigerate for meal prepping.