This is actually a cross between two traditional Japanese dish--sansai udon and ohitashi--to create something that isn't quite either but I think takes some good elements from both.
The common element between the two is greens--komatsuna commonly--and a soy-dashi broth. I created a somewhat richer and more complex broth by caramelizing (or at least browning. I haven't got the patience or temperature control on my stove to properly caramelize onions.) half an onion and then sautéing the CSA oyster mushrooms until they'd browned a little and started releasing moisture. Then I added:
4 cups water
2 teaspoons instant dashi crystals
4 Tablespoons soy sauce
2 Tablespoons rice wine
4 teaspoons mirin, and
2 teaspoons sugar.
Once I had brought that to a simmer I added a pack of udon noodles and cooked for the three minutes recommended on the package. Then I fished those out and set them aside.
Then into the broth went the thicker komatsuna stems and six ounces of deep fried tofu. You can buy pre-fried tofu, but the stuff you buy is puffy and I prefer the chewy texture of homemade. The six ounces is half a standard block of tofu. After a minute of simmering I added the komatsuna leaves, waited until they wilted down, and then turned off the heat and let them soak for ten minutes. One of the recipes I drew from instead left the komatsuna whole and had you tie the leaves into a bunch with butcher string and dangle the stem ends in the broth for a minute before dropping the leafy ends in too. I didn't really have room in my pot for that, but it's an interesting idea.
After the ten minutes are up, warm the soup back up and put serving portions of the noodles into individual bowls. Once the soup's at serving temperature, add greens and tofu to each bowl, ladel over the soup and garnish with scallions, garlic chives and shredded nori.
I accidentally deleted my first draft (first time since starting the blog which isn't a bad run) so I don't have a detailed description of my impressions of the dish when I ate it last Thursday. The broth, I recall writing, was rich and complex, having absorbed flavors both from the onion and mushroom but also komatsuna. The noodles, greens and tofu each absorbed some flavor from the broth too, but not so much that they lost their own distinctive flavors. There's a nice variety of textures in the bowl too. I particularly liked how the tofu squishes out stock when you chew it. It's a tasty and pretty hearty dinner considering the lack of meat (beyond a bit of fish in the dashi).
Another interesting idea in one of the source recipes was, instead of udon, cooking rice in the broth. I tried that the following day but was a bit disappointed in the result as a lot of the broth's flavor disappeared, locked away inside the rice. Plus the rice got kind of mushy. That's probably more because of my rice cooker's sensors getting confused than anything inherent in the broth, though. I did like the suggestion in that recipe of adding a beaten egg to the rice when it was just about done cooking, but you'd be better served adding an egg to the noodle variation.