Smoked Mackerel Potato Dauphinoise
Updated: Feb 25, 2022
“Look at that moon. Potato weather for sure."
Thornton Wilder (1938)
I was given this idea by Martin Yorwarth who brings his catch to one of the local farmers' markets. It was summer when we talked about it and we both agreed that, as a dish, it would be very much in place during colder months. That said, smoked mackerel is available throughout the year, as are potatoes, though the available potato varieties change with the seasons. And that is important as the waxy potatoes more abundant in the summer months are unsuitable for this dish. Currently, one of my favourite potato varieties is called "Sagitta", a floury variety that make incredible chips and which I was introduced to by one of the crew of Ted's Veg who bring them to the market. They work very well here.
I don't know exactly what recipe Martin had been served by his friend, but it seemed to me that simply adjusting a trusty classic Dauphinoise recipe to include chunky flakes of smoked mackerel beneath the bubbling surface ought to do the trick. That and a hint of horseradish which complements smoked fish so well. The result has been very pleasing, and it has only really been a matter of experimenting with different cooking times and temperatures to reach quite quickly a recipe I'm delighted to share.
I've often thought a Dauphinoise to be a quite satisfying main course in its own right. With the inclusion of the smoked mackerel it certainly is and need only be accompanied by a green salad dressed with a simple vinaigrette made with vinegar that has been infused with garlic.
Broadly speaking there would appear to be two methods for preparing a potato Dauphinoise. Probably the more traditional is to cook the dish completely in the oven with the potatoes having gone in raw. The second approach takes rather less time as the potatoes are warmed in the hot milk and cream before being spooned into the gratin dish that then goes in the oven until the cooking of the potatoes is complete.
With the inclusion of the smoked fish I thought it best to work from a recipe following this second approach and the one I have used is one I found in "Foolproof French Cookery", by Raymond Blanc OBE. The recipe calls for the potatoes to be sliced with a mandoline which is of course the ideal method but, not wishing to sound like a bore, do so with care - I'm aware of some rather nasty accidents!
To help with the speed and evenness of cooking I've suggested an idea that I always use when baking pastry cases. That is to pre-heat a baking sheet in the oven for the gratin dish to sit upon, with the aim of speeding up the heating of the base of the gratin dish, which would otherwise naturally be the coolest part of the dish for most of the cooking time.
And when it comes to the cooking time, I'd suggest allowing for more time than you might first think as a dish like this only really fails if undercooked and different varieties potatoes and the thickness to which they have been sliced will have a marked impact. The tip of a sharp knife is the best barometer of readiness but, for completeness, the cooking times given in the recipe are for Sagitta potatoes sliced 3mm thick using a mandoline.
Smoked Mackerel Pommes Dauphinoise
Ingredients (Serves 2)
250g potatoes, peeled and very thinly sliced (weight given is after slicing)
125-150g smoked mackerel fillet
175ml whole milk
125ml double cream
Nutmeg, 4 gratings
1 tbsp horseradish sauce (optional)
½ garlic clove, peeled
Salt and freshly ground white pepper
Preheat the oven to 140°C. Place a baking sheet in the oven to heat up.
Remove the skin from the mackerel fillet and break the flesh into big flakes.
Bring the milk and cream to the boil in a saucepan then add the potatoes, coating them with the milk and cream mixture. Season with the nutmeg, salt and freshly ground white pepper and simmer for 10 mins. Remove from the heat and stir in the horseradish sauce, if using. Check and adjust the seasoning.
Rub the base and sides of an 18cm gratin dish with the garlic then put a thin layer of the potatoes over the base of the dish along with a little of the milk and cream. Scatter the mackerel flakes evenly on top of the potatoes then cover with the remaining potato slices, arranging them neatly for presentation. Pour the remaining milk and cream over the top, allowing it to fall to the bottom of the dish.
Place the gratin dish on the baking sheet and transfer to the preheated oven for approximately 45 mins until the potatoes barely resist the tip of a sharp knife. To brown the top, place under a hot grill for about 5 mins until bubbling and golden. Leave to rest for 5 mins before serving.
"Foolproof French Cookery", Raymod Blanc (2002), pp. 92: https://www.amazon.co.uk/Foolproof-French-Cookery-Raymond-Blanc/dp/0563534648