Sweat the aromatics: Heat the oil in a heavy pot over medium heat. Add onion and a pinch of salt. Cook 3–4 minutes until translucent. Stir in garlic and ginger; cook 30 seconds until fragrant.

Build the base: Add gochujang and gochugaru. Stir for 30–45 seconds to bloom the chili paste and flakes. This step deepens the flavor.

Deglaze and simmer: Pour in the broth, scraping up any browned bits. Add soy sauce and the white parts of the green onion. If using potato, add it now. Bring to a gentle boil, then lower to a simmer for 8–10 minutes.

Add veggies and tofu: Stir in mushrooms, zucchini, and tofu cubes. If using kimchi, add it now along with a spoonful of kimchi juice for tang. Simmer 6–8 minutes until vegetables are tender.

Add protein (if using): Slip in thinly sliced beef, pork, chicken, or shrimp. Simmer just until cooked through. Keep it gentle—overcooking will toughen the meat.

Season and balance: Taste the broth. Add sesame oil, a pinch of sugar or honey if it feels too sharp, and more soy sauce or salt if needed. Adjust heat with additional gochugaru.

Finish with an egg (optional): Crack an egg directly into the simmering soup and poach for 2–3 minutes, or whisk an egg and drizzle it in for silky ribbons.

Garnish and serve: Ladle into bowls and top with the green onion tops. Serve with hot steamed rice and extra kimchi on the side.