In a separate pot, I boiled 1 cup mirin, turning down to simmer and adding 1/4 cup soy sauce and 1 1/2 cups water. Other ingredients were: almost 2 cooked and diced pork chops (Oscar must've taken a HUGE bite during a break from his Madden football gaming session late last night). I chopped and added to the mirin-soy simmer: 4 heads baby bok choy, and 1/2 white onion.
I worried the pork would toughen up since it was already cooked, but figured the flavors would meld in the few minutes. Total simmer time was around five minutes.
One mystery note: a good two teaspoons of wasabi powder added to the mirin simmer at the end of cooking had no flavor or effect.
Once the noodles were finished and rinsed, I ladled them into a bowl, with the mirin broth and vegetables. The broth seemed too sweet throughout cooking, but a sprinkling of toasted white sesame seeds before eating helped.
When he ate the soba for dinner tonight, Oscar detected a subtle wasabi note that wasn't overpowering in the broth.
Next time, I may forgo the pork and add spinach and a sliced boiled egg garnish.