Dolsotbab is a traditional Korean way of cooking rice in a very hot stone pot. The heat of the stone rapidly cooks a single serving of rice. Nurunji is a way to prepare and eat the sometimes burnt but definitely over-cooked rice that remains adhered to the sides of the pot.
Foodies might be all into this for the experience but for me it reveals a bit of social engineering.
Preparation of rice in non-stick pots or steam cookers is a fairly
modern addition to the kitchen. Regular pots are still a bit messy,
prone to overheat and so are only a slight advance over the old stone
bowls heated on a fire. Making another dish to add to the meal out of the scorched remains of the rice is frugal and common sense solution to scarce resources.
Just because the rice may be browned or burnt is no reason to waste it. The preparation of Nurinji requires one to add water to the stone pot, which boils up, softening the burnt rice. The diner then has to put in some work to scrape the scorched rice off the sides and bottom, giving them not only a hot soup but a extra few ounces of rice. Basically the diner does a lot of the pre-soak and cleaning of the bowl which anyone who regularly cleans burnt food off of a pan knows is a bit of a chore. Diners probably get an added bit of minerals in the diet from scraped stone though in the modern era the downside is ingesting aluminum from the flatware flaked off while scraping.
While in the past Nurunji would be created and eaten out of necessity out of being mindful of not being wasteful in an environment where stored food spoiled quickly or attracted pests it has since become a luxury process as a side dish to the modern Korean dining experience.