Miso-soups in Japanese restaurants are sad.
I have been to Sushi, Teriyaki and other places, but I've never had a good Miso-soup bowl. They taste as if they are using instant miso-soup and just dissolving it in hot water. Plus, there is very little ingredients to enjoy. It's all about cost-saving....
Here is the true home made Miso-soup. Put as much as vegetable you want! Nutrition can get the priority at home.
1) Broth, broth and broth.
This is the most important thing for Miso-soup. Please use broth. It can be iriko dashi(anchovy) or katsuo dashi(macharel). If you are vegetarian, konbu dashi (seaweed) will work. All of them are available in ready-to-dissolve package in Japanese grocery stores. Those will be handy as a starter kit.
2) Add broth in boiling water. Try 1-2 tps and see how it tastes.
3) Add your choice of vegetables. Most vegetables work fine. Start from hard vegetables such as carrots, radish or onions because they take longer to cook. Then add another group of vegetables such as cabbage, spinach or other leaves. Tofu can be added with them because it cook quickly and it doesn't taste good when overcooked. To enjoy the vegetables most, boiling time is very important. Not too short, not too long so as the texture and flavor gets just right.
4) Add miso right before you turn the oven off. Miso will lose its flavor when overcooked.
5) My Miso-soup of the day has spinach, red radish, carrots and tofu.