Maangchi's kimchi noodle soup uses fermented, sour kimchi rather than freshly made for the best flavor.
Bring a large pot of water to a boil for the noodles. In a small bowl, mix the kimchi, gochujang, sesame oil, sesame seeds, and sugar.
In a medium saucepan, bring the stock to a boil. Stir in salt. Reduce heat to low. Cover to keep warm.
Add the noodles to the boiling water and cook according to package directions. Drain and rinse under cold water, tossing the noodles until they are no longer slippery. Divide among four bowls.
If using the eggs, in a nonstick skillet, heat the canola oil over medium-high. Add eggs and cook for 1 minute. Cover and cook 1 minute more for medium eggs, 2 minutes more for solid yolks.
Ladle broth over the noodles in each bowl. Top each with an egg, if using, about 2 tbsp. of the kimchi mixture, and some nori. Serve immediately.
Cook the noodles just before serving so they are chewy, not soft. And be sure to use fermented sour kimchi rather than freshly made for the best flavor.
Got some nori left over? Crumble it up and blend with salt, pepper, and sesame seeds to make a toasty rub for grilled meat or a savory topping for popcorn.