Binging with Babish makes Chimichangas

Few improvements I would recommend as someone well acquainted with real deal, New Mexican chimichangas:
For the chicken, one whole chicken roasted and pulled would be better. The combo of light and dark meats makes a much moister and more flavorful chimi.
For the sauce, if you're making it with chicken you should use green chile. Starting with a rue, add chopped green chile, onion, and garlic with some dried oregano and fresh cracked black pepper. Add some chicken stock. Reduce until it begins to thicken and then toss in the pulled chicken and let it continue to thicken and coat the chicken. Then just wrap up with some cheddar and oaxaca.
Chicken pairs much better with the brightness of green chile than it does with the sweet/bitter/chocolatey flavor profile of red chiles.