Hot and sour cabbage soup

Cabbage is one of the only non-root vegetables that is available right now, and it's cheap, so I'm trying to get it into our dinner rotation more often. This weekend I wanted to play around with cabbage soup, and thought that the flavors of Chinese hot and sour soup would work really well. I've eaten hot and sour soup plenty of times at restaurants but had no idea what ingredients gave it its unique flavor, so it was fun to learn how to make it. It's really not that complicated - the ingredients are fairly basic, and the signature hot and sour flavor mainly come from white pepper and vinegar.

I started with a recipe from Gourmet Today and adapted it quite a lot, simplifying the ingredients (e.g. shiitakes instead of more obscure Chinese mushrooms), adding cabbage, using only 1 pot, and making it vegetarian. It came out really good - way, way better than the downright bland version I got last time I ordered Chinese takeout. How on earth did they make a bland hot and sour soup? I can't understand it. Anyway, I'm definitely glad I don't need to depend on restaurants anymore to get some!

Hot and sour cabbage soup
Adapted from Gourmet Today
Serves 6 as a first course

6 dried shiitake mushrooms
1 pound cabbage (about half of a medium cabbage), cut into 1/4-inch ribbons
1 1/2 tbs cornstarch
2 tbs red wine vinegar
2 tbs rice vinegar
1 tbs soy sauce
1 1/2 tsp sugar
1 tsp kosher salt
2 tbs peanut, canola, or vegetable oil
4 cups chicken stock or reduced-sodium broth
3-4 ounces firm tofu, rinsed, drained, and cut into 1/2-inch cubes
2 tsp Asian sesame oil
1 1/2 tsp white pepper (preferably freshly ground)
2 tbs thinly sliced scallions (green parts only)
2 tbs roughly chopped cilantro leaves

Soak mushroom in 1 cup of boiling water for 30 minutes. Meanwhile, stir together vinegars, soy sauce, sugar, and salt in a small bowl until sugar and salt are dissolved.

Remove mushrooms from soaking water, squeezing out excess liquid. Chop mushrooms into bite-sized pieces, removing any tough stems. Mix together 1/4 cup of the mushroom soaking liquid with the cornstarch in a small bowl.

Heat peanut oil in a heavy 3- to 4-quart pot over high heat until hot but not smoking. Add mushrooms and stir fry for 1 minute. Lower heat to medium-high and add cabbage. Cook until cabbage is reduced to 1/2 of its original volume, about 5-6 minutes, tossing frequently. Add stock and bring to a boil. Add vinegar mixture and simmer for 10 minutes, partially covered, until cabbage is tender but not mushy. Add cornstarch mixture and simmer uncovered for 1 minute. Stir in tofu, white pepper, and sesame oil, and simmer 2 minutes longer. Remove soup from heat and season to taste with salt. Sprinkle soup with scallions and cilantro before serving.