Baked Cod with Crithmum (Sea Fennel)

The recipe is taken from the book "Scandinavian Summer". "I believe in quick and easy cooking on weekdays, especially in the summer when you want to spend as much time as possible outdoors. Cod with mustard in various variations is popular all over Scandinavia. This recipe requires only about three minutes of preparation plus baking time, when the fish is briefly cooked in the oven, and you can make side dishes for it. I usually choose various greens, although many people prefer mashed boiled potatoes with butter and parsley. Crithmum grows off the west coast of Denmark, in salty bays, and all along the North Sea coast from Norway to Sweden and Finland. Oddly enough, I did not like it while living in Scandinavia, but in the UK, critmum has recently become so popular that I tried it, and it has taken pride of place in my diet. I love it - it's full of all sorts of useful things and practically no calories. It's also naturally salty , so salt it very moderately.