Thinly slice the onion and trim the root of the shimeji mushrooms, separating them.

Heat 10g butter in a pan over medium heat. Once half melted, add the onion and sauté until softened. Add the shimeji mushrooms and stir until coated with butter. Add the shrimp and cook until they change color. Transfer to a bowl.

Clean the pan and melt 30g butter over medium heat. Add flour and curry powder, stirring until the mixture loses its powdery texture. Gradually add milk while stirring over low heat until thickened. Return the sautéed ingredients to the pan, season with salt and pepper, and mix well.