We’re nearing the end of the green asparagus season around here, so I’m trying to eat as much of it as possible. This miso marinated asparagus dish may look very spicy, but it’s only mildly so - it just looks rather hot because I used a red miso. The miso marinade does not overwhelm the asparagus flavor, but just enhances it. It is great in a bento since it’s salty, a little sweet and spicy all at once.
This recipe is adapted from a Japanese cookbook, Tsukemono Hyakka （漬け物百科）  (Pickling Encyclopedia). Actually the term tsukeru（漬ける）refers to both pickling and marinating, so I guess it could be called the Pickling and Marinading Enclopedia.
Cook the asparagus in boiling salted water until crisp-tender. (To cook them evenly, put the stalks in first, cook for a few minutes, then add the tips and cook for 2-3 minutes more.) Drain and run under cold water to stop the cooking and to fix the green color. Drain well.
In the meantime, sauté the chopped onions in the oil until limp. Add the red chili paste and stir. Add the sugar and mirin, then add the miso. If it gets a bit stuck to the pan, add a few drops of water and stir and scrape to deglaze the pan. Take off the heat.
Add the aspargus and mix well so each piece is coated with the marinade. Layer into glass or ceramic bowl or container (not plastic, because the miso and chili will stain it) evenly. Cover with kitchen parchment paper, then put another bowl or container filled with water; this acts as a weight. Here I’ve used two identical glass bowls; the asparagus is layered in one, covered with parchment paper, then weighted down with the other bowl which is filled with water.
Leave the asparagus to marinate for at least an hour - you can leave it in the refrigerator overnight. Take off the weight and store the asparagus in a tightly covered container.
The asparagus will keep for a couple of days in the refrigerator, but it will gradually lose its green color so you should try to eat it up as soon as possible. This is not that hard to do. (It’s pretty good mixed with hot pasta.)
You can halve the amount of marinade, and marinade just half a bundle of asparagus and use the rest of the cooked stalks for dinner.
Many cuisines call for a red chili paste of some sort. Here I’ve used doubanjang, which is a Chinese (Sichuang) chili paste; you can find it at Asian/Chinese or Japanese grocery stores (in Japan it’s called toubanjang and is written 豆板醤). You could substitute harissa or other red chili paste here. (At one point I had two kinds of harissa, two kinds of doubanjang, and a Hungarian chili paste in the fridge, which was a bit much.) Korean kochujang is a bit less intense, so you may want to double the amount to 2 teaspoons if you use that.