These are delicious sandwiches. Use vegetarian Worcestershire sauce. I have tried making these also with fresh mozzarella and American cheese, but the fontina is wonderful. Also, it's good to prepare eggplant before cooking. Slice, salt both sides and place on a paper towel on a plate. Put a paper towel over the slices and place another plate on top and then place something heavy on top of the plate. This helps draw out eggplant's natural bitterness and allows you to get away without using so much oil to cook it with. After an hour or so, remove the eggplant and brush off the salt and use. I've also heard of people rinsing off the eggplant but I've never rinsed it.