Varm Røget Makrel med Kartoffelsalat og Dildsmør

Ingredients

Equipment Needed

• •Large saucepan for the potatoes
• •Baking tray
• •Mandoline for the onions
• •Large oval serving platter
• •Small mixing bowl for the dildsmør
• •Cling film for shaping the butter

Instructions

1. 1

   Pickle the onions

   Start here because the onions need time. Slice the red onions as thinly as you possibly can. A mandoline is the right tool. Thick slices stay too sharp and fight the fish instead of balancing its richness. Place the rings in a small bowl, pour over the white wine vinegar, and add the sugar and salt. Stir once and leave them alone for at least fifteen minutes while you prepare everything else. The vinegar draws out the raw bite and turns the edges translucent and pink. They'll get better the longer they sit.

   If you have time, make these a few hours ahead or even the night before. Overnight pickled onions lose all their harshness and become sweet and almost silky. They'll keep in the fridge for days.
2. 2

   Boil the potatoes

   Put the nye kartofler into a pot of well-salted cold water. Starting in cold water matters: it lets the potatoes heat evenly from the outside in, so you don't end up with soft edges and a chalky center. Bring to a gentle boil and cook until a knife slides through the middle of the largest potato without any resistance at all, about fifteen to eighteen minutes depending on their size. Don't rush this. An undercooked potato at the center of your salad announces itself on the first bite. Drain and let them sit in the colander for five minutes, just until you can handle them. You want them warm, not cold.

   If you can find true nye kartofler, the small waxy new potatoes of Danish summer, leave the skins on. They're thin enough to eat and they hold the potato together in the salad. Larger potatoes should be peeled and halved.
3. 3

   Make the dildsmør

   While the potatoes cook, beat the softened butter in a bowl until it's creamy and light. Fold in the finely chopped dill and a good pinch of flaky sea salt. If you're using lemon zest, add it now. The lemon doesn't make the butter taste of lemon. It lifts the dill and sharpens the edges just enough to stand up against the smoky fish. Mix until the dill is evenly distributed and the butter has turned pale green. Spoon it onto a piece of cling film, shape it into a rough log about four centimeters across, and twist the ends tight. Put it in the fridge to firm up. You want the dildsmør cold and solid when it meets the warm mackerel. That contrast is half the pleasure: the butter softens slowly against the hot fish, releasing the dill as it melts into golden-green pools on the plate.

4. 4

   Dress the kartoffelsalat

   Cut the warm potatoes into halves or thick slices, depending on size. Put them in a wide bowl. In a smaller bowl, mix the crème fraîche, mayonnaise, and Dijon mustard together until smooth. Pour this over the warm potatoes and turn them gently through the dressing with a large spoon. This is important: dress them while they're warm. Warm potatoes absorb the dressing and it becomes part of them. Cold potatoes just sit under it, and the salad tastes flat. Add the chopped dill and snipped chives, season well with salt and white pepper, and fold everything together once more. Taste it. The dressing should be tangy and clean, the herbs visible throughout. Let the salad sit at room temperature while you warm the fish.

   Don't be heavy-handed when you stir. You're coating the potatoes, not mashing them. A few gentle folds with a large spoon keep the pieces intact and give the salad its character.
5. 5

   Warm the mackerel

   Heat the oven to 150°C. Place the whole smoked mackerel on a baking tray lined with parchment. Warm them for ten to twelve minutes, no longer. You are not cooking the fish. It is already cooked. What you are doing is bringing it back to the temperature where the oils loosen and the flesh becomes silky and yielding again. Too much heat and the fat renders out, leaving you with dry, fibrous fish that sticks to the skin instead of flaking away from it. You'll know they're ready when the skin tightens slightly across the body and the aroma of alder smoke fills your kitchen. That smell is the signal. Trust it.

   If your mackerel came from the fishmonger's fridge, give them an extra two or three minutes. Straight from the cold they need a little longer to warm through. But watch them. Once the skin starts to split, you've gone too far.
6. 6

   Assemble the plate

   This is where it all comes together, and the composition matters. Set the whole warm mackerel on a large serving platter, leaving room on all sides. Spoon the kartoffelsalat alongside in a generous, informal mound. Slice the chilled dildsmør into thick rounds and place them directly on top of the warm fish, where they'll begin to soften immediately. Drain the pickled onions and scatter them over and around the mackerel. Lay a few sprigs of fresh dill across the plate and tuck lemon wedges into the gaps. Bring the rugbrød to the table on a separate board, sliced thick. This plate arrives all at once, warm and cold together, and everyone helps themselves. The mackerel skin peels back to reveal the golden flesh. The butter melts. The pickled onions cut through the smoke. Cooked with love, served at a table where people linger. Tak for mad.

Chef Tips

• •Look for hot-smoked mackerel, not cold-smoked. Hot-smoked mackerel is firm and opaque and flakes into moist chunks when you break it open. Cold-smoked is translucent and silky, more like smoked salmon. For this plate you need the hot-smoked kind, the one that comes whole from a Bornholm røgeri or a good fishmonger. If the label says 'varmrøget,' that's the one.
• •Dress the potatoes while they're warm. I can't stress this enough. The difference between a kartoffelsalat dressed warm and one dressed cold is the difference between potatoes that taste of the dressing and potatoes that merely wear it. Five minutes out of the water is the right moment.
• •The dildsmør must be cold and firm when it goes on the warm fish. The whole point is the contrast: watching it soften and melt against the mackerel, releasing the dill into golden-green pools. If the butter is already soft when you plate it, you've lost that moment. Make it ahead and keep it in the fridge until the last second.
• •Use fresh dill, not dried. Dried dill is a different ingredient entirely, dusty and dull where fresh dill is bright and alive. In Danish cooking, dill is used the way the French use parsley: generously, everywhere, without apology. Buy more than you think you need.
• •Serve this with cold Danish pilsner or a glass of dry white wine. Akvavit is welcome if the mood calls for it, but this is a summer plate, relaxed and unhurried, and a cold beer in the afternoon sun is hard to improve on.

Advance Preparation

• •The dildsmør can be made up to three days ahead. Keep it wrapped tightly in the fridge. The dill flavor actually deepens overnight, so making it in advance is a gift to yourself.
• •The pickled onions improve with time. Make them the night before if you can. They keep well in the fridge for up to a week.
• •The kartoffelsalat is best made the same day, dressed while the potatoes are warm. It holds well at room temperature for an hour or two, which makes it perfect for outdoor dining or a picnic spread.
• •Warm the mackerel just before serving. This is the one step that cannot wait. Cold smoked mackerel is a different dish entirely, good in its own way, but not this plate.

Frequently Asked Questions

Nutrition Information

1 serving (about 510g)