Korean maeuntang usually is made with anchovy stock, chrysanthemum greens and a whole fish that's been cut into pieces. And it's typically brought to the table simmering in a wide, shallow pot. Our simplified version uses store-bought broth, baby spinach and cod fillets, all cooked in a Dutch oven, but it still gets fiery notes and lots of umami from gochujang, a Korean fermented chili paste. Soy sauce, sesame oil and plenty of garlic and ginger round out the flavors. Serve with steamed white rice.