Wash the spinach. Boil or microwave, then put into a bowl of water. Wring, cut into about 1 cm pieces, and set aside.
Bring 700 ml of water to a boil in a pot. Add soup stock and dashi stock. Add sliced onions and cook on low heat until transparent. If you cook on high heat, the onions start to melt.
Once the onions have boiled, add katakuriko dissolved in a tablespoon of water and mix (this doesn't cause creaminess).
Increase to high heat, and once it's simmering, add the beaten egg a little at a time as shown in the picture. Check and make sure the soup is boiling properly. You should get an eggy texture that looks like the picture shown.
Caution: If the soup isn't simmering, the soup will be cloudy. If you just drop the egg in it becomes bunchy, like a jellyfish.
Lastly add the spinach and bring to a boil. Flavor with coarsely ground pepper and it's complete.
This is what it looks like. The soft, expanded egg looks great.
Story Behind this Recipe
I wanted to make a soup that would go well with white rice.
By adding just a little starch, not enough for it to become creamy, the egg spreads out nicely. I don't have hints in particular. Well, if I can say one thing, mix the egg well and set aside. Add the spinach right before you eat. It will discolor if left boiling for too long.