Warm oil in an Instant Pot on saute mode until it begins to smoke.
Add the pork in a single layer and let it brown for 3-4 minutes. Repeat with the remaining pork, and set it aside.
Next, add the onions, guajillo chilies, and ancho chilies. Cook until they blister, then add them to a food processor or blender along with water and Better Than Bouillon.
Add the remaining ingredients, chili mixture, and pork. Stir to incorporate. Secure the lid on the Instant Pot and cook on manual high pressure for 50 minutes with a 10-minute natural release.
Using tongs, retrieve the garlic head from the broth. Squeeze the garlic head to release the cloves into the broth, and whisk to combine.
Garnish with red radish, red onion, cabbage, cilantro, lime wedges, avocado, chili flakes, cotija cheese, and Mexican oregano. Serve with corn tostadas.
Notes
Nutrition Disclosure:
The nutritional information shown is an estimate provided by an online nutrition calculator. It should not be considered a substitute for professional advice.