Slice the onion thinly, remove the base of the shimeji mushrooms and separate them by hand, and mince the garlic after removing its core.

Heat butter in a pot, add garlic and onion, and sauté over medium heat until softened. Add shimeji mushrooms and cook until tender. Add water and bring to a boil, then cover and simmer on low heat for 5 minutes.

Turn off the heat, add curry roux, and stir until dissolved. Once dissolved, heat over medium heat until boiling, then add baby scallops and simmer on low heat for 3 minutes, stirring occasionally.