Rinse clams in a bowl of water, rubbing them together to clean thoroughly. Drain the water.

Remove the stem from the tomato and cut into bite-sized pieces. Slice king oyster mushrooms thinly after halving them vertically and horizontally. Slice garlic thinly and remove the core.

Heat salad oil and garlic in a frying pan over low heat until fragrant. Add chili and mushrooms, stir-frying over medium heat until coated with oil. Add tomato and stir-fry for 1 minute.

Add clams and sake, cover with a lid, and cook over medium-low heat for 7–8 minutes until clams open.