Boil and shred chicken with a fork. Preheat the oven to 350 degrees.
Combine flour and butter in a pan over medium heat. Cook for a couple of minutes, this will be for the rue. At this point add the chicken stock, once thickened, like thin gravy, take off the heat and add the salsa and sour cream. Stir until mixed together, put aside while you assemble the enchiladas.
Put about 1/4 cup or so of shredded chicken onto a flour tortilla and then top with about 1/4 cup of shredded cheese on as well, just enough so you can tightly roll the tortilla up tightly. (When the kids will not be eating I use Pepper Jack for a little more depth of flavor.) Roll the tortilla and place in a 9 by 13 1/2 backing pan. Repeat until the pan is full.
Once done with rolling the enchiladas pore the white sauce onto the enchiladas. With a spatula gently separate the enchiladas so the sauce seeps in-between and lightly under neath them so the bottom of the enchiladas so they don't burn in oven. Sprinkle reaming cheese on the top.
Place in over for forty five minutes. Let cool for five minutes and serve. Great with side of guacamole, salsa, sour cream and tortilla chips.