Boil water in a pot, add shungiku, and cook for 1 minute. Drain, squeeze out excess water, and cut into 3cm pieces. Dice onion and potato into 1.5cm cubes, and soak potato in water before draining.

Prepare a bowl of salted water. Wash oysters gently, changing water 2–3 times, and pat dry with paper towels.

Place oysters and white wine in a microwave-safe container, cover loosely with plastic wrap, and microwave at 600W for 2 minutes. Separate the oysters from the cooking liquid.

Melt butter in a pot over medium heat, add onion and potato, and sauté until softened. Add flour and cook until no raw flour remains.

Add water, consomme, and the reserved oyster cooking liquid. Stir and bring to a boil, then cover and simmer on low heat for 10 minutes.