Preheat the oven to 400F.
Warm tortillas on top of the stove for few seconds, it will make them soft and flexible.
In a mixing bowl combine chicken, ground cumin, cheese, chillies, Mexican White Sauce, salt and pepper. Give it a good mix.
Place 1/2 cup of the chicken mixture on center of each tortilla. Fold the sides, then the bottom side up, to cover the filling, roll over to create chimichangas.
Brush each chimichangas with butter and bake for 15-20 minutes or until golden color. Serve with additional white sauce and salsa.