In a medium sauce pot, combine stock, kelp, onion, garlic, cucumber and 1 cup of water. Bring the mixture to a boil and simmer for 5~6 minutes.
Add the chopped bok choy/ spinach and scallions. Cook for another 2~3 minutes.
Take the miso in a small bowl and add 2~3tbsp of the boiling stock. Mix well to combine thoroughly.
Add the miso paste to the boiling soup. Mix well to combine, season with salt and pepper. Turn off the heat and serve hot with Joomuk Bap (Fist Balls).