Thinly slice the onion. Peel and cut the potatoes into bite-sized pieces. Soak in water, drain, and microwave for 6 minutes at 600W. Drain again.

Place oysters in a bowl with potato starch and gently rub. Rinse with water, changing it three times, and pat dry with paper towels.

Lightly coat the oysters with all-purpose flour.

Heat olive oil in a pan over medium heat. Add oysters and cook both sides. Add sake, cover, and steam for 3 minutes. Remove oysters from the pan.

In the same pan, melt butter over medium heat. Add onions and sauté until soft. Stir in flour and cook until no longer powdery. Gradually add milk, salt, pepper, consomme, and potatoes. Cook until thickened, then return oysters to the mixture.