Hard to tell from your description, but it sounds like the kinds of recipe a typical Sanuki Udon-ya would make way back. Do you remember anything about the spice? Was is red and kind of peppery like Shichimi tōgarashi (Japanese: 七味唐辛子, "seven flavor chili pepper")? Or something else?
Udon is actually very simple but can be garnished almost in infinite varieties. I've had some that was just udon, soy sauce, and chives.