This sandwich is so very yummy. The cheese is a cashew cheddar from a recipe I found at Vegan Epicurean. I've made this "cheese" three times. It's melty just like real cheese and tastes great on sourdough bread. You will need raw cashews, nutritional yeast, and agar powder. You can change the spices, but so far I've followed the recipe as given.
Agar-agar is a sea vegetable by-product that is used like gelatin. Look for agar-agar powder in oriental markets. A packet of Telephone Brand agar-agar powder (from Thailand) is between .99 and $1.50 at the oriental markets locally. If you're unable to find it in your area, you can also buy different brands of agar-agar powder online.
This is what my loaf of "cheese" looks like. I slice it in six pieces and store in a plastic container in the refrigerator. It will last a week...IF you don't go on a grilled cheese binge. Heh.