I wanted to try this out for ages but it wasn't until very recently that I found a shop selling the requisite Swedish anchovies, which are actually sprats pickled in a quite sweet brine. Swedish ansjovis (sprats) are, I think, reasonably good on the marine conservation stakes, being mature fish when they are caught.
They are also pretty healthy, containing lots of omega oils. If you frame it with the high levels of vitamin A in the cream, plus vitamin C and B6 in the potato, this isn't a totally unhealthy dinner... but saying that, it's carb heavy and contains double cream so it's probably not an everyday dinner! This would go really well with a lovely side of steamed spinach or broccoli.
So first up, dice two onions and saute them in a little oil and a little butter. While that's cooking, thinly slice several potatoes - it's important that they are really thin or they won't cook through.
Open up the tin of ansjovis and cut each one in half, then butter an oven proof dish and preheat the oven to 180°C. Take the frying pan off the heat and divide out half of the onions, you'll use half now and half in the creamy sauce later on.
Put a layer of potatoes on the bottom of the dish, sprinkle with onion and then lay peices of fish over the top. The, another layer of potatoes, more onion, more fish and so on until all the fish, potatoes and half of the onions are used up.
Put the frying pan back on the heat with the second half of the onions still in there, add half a pot of crème fraîche and half a pot of double cream, stir until melted together and season well with sea salt and freshly ground white pepper. Pour over the top of the potato-onion-fish layers.
Then the crispy topping - I use crackers, as in cheese and biscuits! Left over crackers, water biscuits and so on are perfect all crumbled up and sprinkled over the top. Dot with lots of butter and then bung in the oven for 40-50 minutes. Poke it with a fork to see if the potatoes are done.
* I bought my ansjovis when I went to the Scandinavian Kitchen shop one Saturday. The base inspiration for the recipe above came from Scandalicious by Signe Johansen