Smoked Mackerel Gratin

Preheat the oven to 200C/390F and lightly grease the oven proof dish.
Place potatoes and garlic in a saucepan and cover with cold water. Bring to a boil then simmer for 10 minutes. You should be able to get a sharp knife through them but they not be falling apart. They will finish cooking in the oven. Drain the pan and remove the garlic.
While the potatoes are cooking, peel the skin off the mackerel and flake the flesh straight into the dish, carefully pulling out any bones which may have been left behind. Leave the fish in quite large chunks if you can.
In a cereal sized bowl, whisk the creme fraiche to loosen it, then stir in the mustard and whisk again. Mash in the soft garlic and slowly whisk in the milk, a little at a tie to avoid lumps. Then stir in the herbs.
Cover the fish with the hot potatoes, then pour over the creme fraiche and mustard mixture and top with the grated cheese and a grinding of pepper.
Bake in the oven for about 25 minutes.
Scatter over a little more chopped parsley and serve with a green salad with a mustardy dressing and some crusty bread to soak up the delicious juices.
Notes - You could add a scattering of halved cherry tomatoes before covering it with cheese and you could also add a layer of fresh spinach leaves (which you have run under a tap to make wet) under the fish in which case you should increase the milk by about a 1/4 cup.rnrnThe smoked mackerel is quite salty as is the cheese so you shouldn't need any additional salt.