Place half of the cheese on 2 slices of bread. Tear the nori sheets in smaller pieces and add to the cheese. Top off with more cheese and the slices of bread.
Grill the sandwiches until the cheese is melted and the bread is brown and toasted. If you don't have a grill, you can also bake the sandwiches in some olive oil or butter in a regular pan.
Making the sauce
Whisk the mayonaise, soy sauce and sesame oil in a bowl. If you like spicy, you can add some chili oil or dried chili as well.