Preheat oven to 350 degrees. Prepare a 9 x 13 baking dish by spraying with non-stick coking spray.
Chop the cooked chicken into small bite-size pieces.
Combine chicken, cheese and sour cream until well blended.
Scoop about 1/4 cup chicken mixture into the center of each tortilla. Roll the tortillas into a cigar-shape, enclosing the chicken filling. Lay close together in the baking dish, seam side down.
Saute the minced onion and garlic in the oil over medium heat. When the garlic is fragrant and the onion has softened add 2 cups chicken broth and bring to a boil.
Add the can of rotel, with all of the juice. While the mixture returns to the boil combine the cornstarch with the remaining chicken broth, mix well then stir into rotel mixture. Simmer for a couple of minutes to cook out the raw cornstarch and thicken the mixture.
Spoon the hot sauce over the rolled tortillas making sure to cover all of the tortillas (don't leave any dry spots or they may burn).
Place the pan in the oven and bake for 20-25 minutes or until the sauce is bubbly and the tortillas are hot throughout.
Feel free to adjust the seasoning in the chicken mixture and/or the sauce to your taste. I like to use the rotel tomatoes with cilantro and lime. Sometimes I saute sliced, fresh jalapenos or serranos with the onion when making the sauce, etc. Depends on my mood when I make it. The cheese and sour cream usually make the filling salty enough for me, but I often add cayenne or chili powder and black pepper if I want a bit of bite. Sometimes I use pepper-jack cheese for all or part of the cheese in the filling.