Cut spinach into 4cm pieces, slice the onion, and separate shimeji mushrooms into smaller pieces.

Cut salmon into bite-sized pieces, season with salt and pepper, and coat with flour.

In a pan, add 100ml water and spinach. Cover and cook on high heat until wilted. Remove, rinse under cold water, and squeeze out excess moisture.

Clean the pan, heat salad oil, and cook salmon skin-side down on medium heat until both sides are golden. Remove and set aside.

In the same pan, melt butter and sauté onion and shimeji mushrooms on medium heat until softened.

Add flour for the sauce and stir until no longer powdery.

Gradually add milk, water, miso, and dashi powder, stirring until the sauce thickens.