I named this the Costco sandwich because I bought all of the ingredients at Costco. If you don't live by a Costco, you can still find these ingredients at most grocery stores. Good pesto is hard to find, but it's also easy to make. Don't you just love the smell of Pesto? I can't get enough of it. It's right up there with baby lotion and new car smell.
I really love hot sandwiches...especially when they involve pesto and melted mozzarella. I made these for lunch one day and then dinner the next day.