Prepare the chicken:If using a whole chicken or chicken pieces, add to a pan or pot with just enough water to cover. Bring to a boil, reduce the heat to a simmer, and cook until completely done (about 20-30 minutes). Remove the chicken and let it sit until it’s cool enough to handle. Remove the skin and bones and discard. Cut the chicken into chunks. If using a rotisserie chicken, remove all skin and bones from the chicken and discard. Cut the chicken into chunks.
Place the chicken in a large bowl and add the broth, soups, and sour cream. Stir until thoroughly combined.
Place the crushed Ritz crackers in a small bowl. Pour the butter over the crackers and toss until combined.
Preheat the oven to 300 degrees. Grease or butter a 13x9 baking pan or casserole dish (or spray lightly with non-stick cooking spray).
Pour half the cracker and butter mixture in the prepared baking dish. Top with the chicken mixture. Add the remaining crackers.
Bake for 25-30 minutes or until bubbly. Remove from the oven
Let cool for 10 minutes before serving.
Notes
Store completely cooled leftover casserole in an airtight container in the refrigerator for up to 3 days.
To reheat, place individual portions in the microwave or oven until heated through. You can also reheat the entire casserole, covered with aluminum foil, in the oven at 350°F for about 20-25 minutes until warmed through.