This is one of those really useful and versatile sauces or pastes (the consistency just depends on how long you cook it down to evaporate the moisture) that is so easy to make that it’s really barely a recipe. It’s a basic standby in Japanese kitchens. As a loose sauce, it can be used in stir fries or as a sauce on meat dishes. As a stiffer paste, it makes a great onigiri  filling. Cook it down more to make it quite dry (though it will still be clumpy, not totally dessicated like commercial furikake), and it becomes an interesting furikake . I’ve given 3 variations for you to try here. The first is the most traditional, the second is low in sugar, and the third is alcohol-free.
Incidentally, it’s either called negimiso or misonegi, depending on who you talk to. Both words mean the same thing, combining the word for onion or leek (negi) with miso. I prefer to call it negimiso.
Loose negimiso can be stored in the refrigerator for about a week, or in the freezer for up to a month. Cooked down paste can keep for a bit longer, and well cooked down, dry furikake can even be kept in the pantry.
Negi is a particular type of bunching onion - that is, an onion that does not form a bulb at the bottom. It’s somewhere in between a leek and a scallion or spring onion in thickness and texture. I have seen it translated as Welsh onion, though it’s not exactly the same. Japanese cooks usually just use the white part of a negi, rather like leeks, but in Osaka they prefer to use the green parts (and the locally available negi are grown to have more green). You can use either leeks, spring/green onions (scallions) or both.
The more salty the miso is, the more salty the negimiso will be of course. Try experimenting with various miso pastes and see which one you like the best. The negimiso in the photo was made with a mixture of red and white (brown) miso. See the Japanese Miso Primer .
All of the recipes make about 2/3 US cup of loose sauce, and a lesser amount of cooked down paste. You can increase the amounts proportionately to suit your needs.
Sauté the chopped up leek or green onion in the oil over medium heat until limp and translucent.
In the meantime, combine the miso, sugar, mirin and dashi stock in a bowl. Add the mixture to the pan. Stir and cook until the sauce is glossy and thick. Take off the heat and let cool.
You can continue stirring and cooking this down until it forms a stiff paste to use as an onigiri filling, or cook it down for a longer time until it turns quite dry. Be careful not to let it burn.
This still has a sweet taste due to the addition of onion, even without adding the sugar substitute. (By onion here, I mean the regular bulb kind.) For diabetics, note that there may still be a little sugar in the miso itself, depending on what kind you use, and the mirin. See more about that here .
Sauté the chopped up onion oil over medium heat for a few minutes, then add the leek or green onion. Keep sautéing until it’s all limp and translucent.
In the meantime, combine the miso, sugar, mirin and dashi stock in a bowl. Add the mixture to the pan. Stir and cook until the sauce is thick - it won’t turn that glossy since there’s no sugar in it. Take off the heat and let cool.
You can continue stirring and cooking this down until it forms a stiff paste or furikake, as for the first recipe.
This one lacks some of the depth of flavor of the first two variations, but is still good! If you want it to taste sweet, add sugar or sugar substitute to your liking.
Sauté the chopped up leek or green onion in the oil over medium heat until limp and translucent. Add the miso, and enough water to make it into a paste. Stir to cook down a bit, and let cool.
You can continue cooking this down, as with the first two variations, in a frying pan. Or you can toast it lightly by spreading very thinly on a greased or parchment-lined baking sheet, and baking for 5 to 10 minutes in a 400°F / 200°C oven. The surface will turn dry and a bit crispy. Scrape it off the paper or baking sheet with a spatula - it will clumpy, not totally dessicated like commercial furikake. This is great as an onigiri filling, or sprinkled on plain rice or even noodles, or on low-key iridofu .
You can make any of the negimiso variations spicy by adding some red chili peppers to the onions as they cook. Or, just add a sprinkle of shichimi tohgarashi (see Essential Japanese ingredients ) for a more complex flavor.