Wash the clams by rubbing them together in water.

Cut a cross into the spinach root and wash by shaking in water. Mince the garlic after removing its core.

Boil water in a pan (about 1/3 of the pan depth), add spinach, cover, and boil for 1 minute. Remove spinach, rinse in cold water, squeeze out excess water, and cut into 4cm pieces.

Rinse the pan lightly, spread spinach in the pan, place clams on top, sprinkle minced garlic, pour sake, and place butter on top. Cover and steam over medium heat for about 5 minutes until clams open.

Open the lid and mix gently.