You should introduce your son to Korean soups/stews. If he likes miso soup that much, he'll find some favorites in Korea as well. I'm especially partial to spicy doenjang jigae (a Korean miso stew--you can mostly use the ingredients recommended to add to the broth as suggestions and use whatever you like because it's all about the broth).

This is very similar to how I make it except that I use packaged dashi and usually use shellfish and leafy greens, sometimes noodles (udon or dangmyeon glass noodles): https://www.beyondkimchee.com/doenjang-jjigae/

It's easier than it sounds. Put dashi packet in water. Heat then remove. Add doenjang, gochujang, garlic and heat up/mix. Add solid ingredients of your choice and heat until cooked through. Add green onions (optional, I guess, but c'mon). Eat.

So good. Thank you, Korea.