Prepare the chicken by mixing 1 1/2 tsp cumin, 1 tsp oregano, 1 tsp salt, 1/2 chilli powder, 1/2 tsp smoked paprika or chipotle paste and pressed garlic. Arrange the chicken breasts at the bottom of the Instant Pot, pour the sauce over and mix to coat the chicken.
Pressure cook in Instant Pot on Manual at high pressure for 8 minutes. Allow for natural pressure release. Take the chicken out of the pot and shred with two forks, bring back to the liquid. Initially it will look like the chicken is swimming in the sauce but give it 10-15 minutes and most of the sauce will get absorbed up by the chicken. Alternatively, you can cook this chicken, covered with a lid or tin foil in the oven at 180C/350F for 40 minutes or until it could be shredded.
While the chicken is cooking make the enchilada sauce. In a saucepan heat the vegetable oil, then add the flour and mix to combine into a paste, then add the ancho chilli powder, onion and garlic powders, dried oregano, salt, ground cumin and tomato paste. Continue cooking it over low heat while stirring. You will have a thick dark coloured paste, which will smell very fragrant.
To that paste add a small amount of chicken stock and stir with a whisk until well blended, then pour in the rest of the chicken stock, bring to a simmer and cook for a few minutes until it thickens slightly. Take off the heat and set aside till needed.
Preheat the oven to 180C/350F. You will need 2 9X13 inch rectangular pans to cook the enchiladas. Add 1/2 cup of the enchilada sauce to the bottom of each pan and spread with a spatula to cover it entirely.
Assembling enchiladas is a messy affair, so wear kitchen gloves if you wish. To start the process, dip each corn tortilla into a hot enchilada sauce, this will soften it and make it more pliable as well as give it flavour. Then lay it on a cutting board and add some prepared shredded chicken filling, then roll it up like a cigar, then place in the pan seam side down. (See photos in the post for reference). Continue until the chicken and tortillas are used up and both pans are full. (If you have leftover chicken, keep it refrigerated and use up in quesadillas.)
Pour the remaining enchilada sauce over the enchiladas, then top them with grated cheddar or Monterey Jack cheese, cover with aluminium foil and cook in the preheated oven for 15 minutes. Then uncover and cook for 5-10 minutes longer until the cheese is bubbly.