There's a little sauce, which is 2 tbsp Veganaise + 1 tbsp sweet relish. The recipe also called for mixing some ketchup in, but (1) I don't have any ketchup and anyway I don't like it; and (2) holy God, the thing tasted so fantastic with just the Veganaise and sweet relish I didn't want to wreck it by adding anything else.
For seitan I used some thin-cut slices of the "chicken" type seitan I raved about a while back, and for cheese some homemade cashew cheese which I believe is more or less the "gooda" cheese from the Uncheese Cookbook without the nutritional yeast. I really like nutritional yeast—it's my favourite topping for popcorn, for instance—but it does something uncomfortable to cashew cheese, in my opinion. That said, my cashew cheese had a pretty good texture but was very bland—in fact, it tasted a lot like what may still be called "farmer's" or "jack" cheese, so basically a little more like nothing than raw tofu.
The really big deal was that I got to use my new panini press, which was a birthday present from back in September, but since Japanese cooking doesn't involve paninis, I wasn't really in a position to play with it until now. I love the way the press cooks sandwiches, but there has to be a way to make great vegan paninis without nearly everything in them imitating some kind of animal product. I will be giving some thought to this in the next little while, but if anyone reading this has any ideas, please pass them along!