I bought too much fluke (flounder) which I used in my matsutake dish. I thought about making menier or grilled or fried flounder but I decided to make this dish. One of the reasons I chose this dish is because I had extra kelp broth left over from when I made matsutake rice.
Broth: Again, this is typical Japanese seasoning combination. I used kelp dashi, sake, mirin, and soy sauce (2:1:1:1). If you like you could add sugar (up to 1 tbs) to this. You must add enough slices of fresh ginger (3-4 thin slices) to add a good ginger flavor to this dish. I placed the seasoning liquid in a flat wide pan like a sauté pan so that the fillets are in a single layer and covered with the seasoning liquid. I gently simmered it for 10 minutes. Since this was a fillet, I did not bother with "otoshi buta" 落とし蓋 but instead, I covered it with a piece of kelp while the fish was cooking.
I served the fish with the kelp on the bottom (as decoration, just becase I had it) and boiled asparagus. I had to admit, this is not one of my favorites but it has a nice gentle texture and the taste of fresh ginger. Oddly, I am already feeling better.
Here is a more classic image of "Karei no nituske" カレイの煮付け（http://www.jf-net.ne.jp/kagyoren/image/santi/12-6.jpg）