Grease your slow cooker insert with the butter, then leave the rest of the butter in the bottom. This prevents some sticking and adds flavor.
Add the chicken and mushrooms, pour the stock in, and sprinkle the Italian Seasoning mix over the top, use two packets for a more seasoned dish. Cover and cook on Low setting for 4 to 6 hours, no peaking until 4 hours have passed, then check the chicken for tenderness.
30 minutes before serving, turn the slow cooker to the High setting, cut the cream cheese into cubes and stir into the chicken and mushrooms, cover and continue on High setting for about 15 minutes, then stir again to fully combine the cheese into the mixture.
Serve with rice, pasta, mashed potato, and a vegetable for a complete meal.