Add oil to the instant pot and put on sauté setting. Once oil is hot add pork pieces. Season with salt and white pepper as it browns, stirring occasionally.
Once meat is browned, add tomatillos, chiles, leeks, garlic, carrots, cumin, and broth, stir to combine. Seal instant pot and place on high setting for 50 minutes.
Release steam and uncover pot. Stir in cilantro and season with more salt, if needed.
To serve, place a handful of mozzarella in the bottom of each bowl, ladle the hot stew over the top and serve with tortilla chips and more sliced chiles.
