Cook the chicken breasts and the jar of salsa in the instant pot (pressure cook for 23 mins if frozen, 15 if defrosted, using natural release).
If you don't have a pressure cooker, simply cut chicken into small pieces and saute with the salsa on stove top.
Shred chicken after cooking. (A hand mixer works great for this.)
Reduce liquid until pretty dry using the saute function on the instant pot, or by sauteeing in the pan.
While chicken is cooking, slice onion and green pepper into thin strips and sautee these on the stovetop.
Assemble flour tortillas with shredded Mexican cheese, the shredded chicken, peppers, onions, cilantro.
Fold tortilla sides in then ends in to get a burrito style shape.
Heat a large pan with vegetable oil and saute the chimichangas on both sides until brown and crispy.
Place the chimichangas in a baking dish, top with shredded cheese and melt in 375 degree oven for 5 minutes before serving.
Serve with cilantro, sour cream, Cholula and jalapeños.