Cook time includes the time to make the sauce. Make sure to leave an inch or so at the top of the dish for the sauce. Mine almost ran over! I also placed the casserole dish on a cookie sheet in case it spilled over (it didn't, but better safe than sorry). With this method (pouring the sauce over all of the potatoes) all of the sauce is on top of the potatoes. If you would like the sauce to be more evenly distributed you can alternate sauce and potatoes when putting it into the casserole dish.