Kohlrabi and smoked mackerel gratin

There comes a time in every food writer’s life when they have to file something about kohlrabi. Cue “looks like an alien“, “German hybrid“, “some people say they don’t taste of much“.

Well, that time for me was a month or so ago for Borough Market’s excellent magazine Market Life. All the boxes were ticked — you should take a look.

For what it’s worth, I don’t subscribe to the view that this veg is pointless; I love it mandolined and macerated, as well as shoved in gratins and stews like a root vegetable (rather than the swollen growth of a wild cabbage species that they are). Though I don’t get the soup recipes.

The recipe below picks up on the gratinated theme, and is perfect for autumn through winter. Wholegrain mustard and lemon cut through the mellow, earthy flavours of cooked kohlrabi and spinach, while the cream and smoked mackerel add extra layers of flavour to the dish. It makes a lovely supper, served with a crisp, refreshing salad and perhaps some fresh bread to mop up the juices.

Long live kohlrabi, and all those who write about it.

Kohlrabi and smoked mackerel gratin

Serves 4

  • 800-900g kohlrabi, including leaves if they’re on
  • 2 smoked mackerel fillets (150g)
  • 200g spinach (large leafed)
  • 300ml double cream
  • 100ml whole milk
  • Juice of ½ lemon
  • 4 tsp wholegrain mustard
  • Sea salt and white pepper

Pre-heat the oven to 220C. Dig out a medium-sized gratin or oven-proof dish—I use a 23cm circular pan, which is about 7cm deep.

Cut any stalks off the kohlrabi and reserve the leaves. Peel with a vegetable peeler, then use a mandolin to slice into 3mm-thick pieces. Put to one side.

Wash the spinach thoroughly, remove and discard the stalks and chop the leaves in half. Put the cream, milk, 1 tsp mustard and a good pinch each of salt and white pepper in a milk pan and warm to a gentle simmer while you assemble the gratin.

Spread the kohlrabi slices in one layer. Smear with 1 tsp mustard. Season with salt and pepper and flake one third of the mackerel over the top. Place a layer of spinach (and the kohlrabi leaves if you have them) over this, then repeat three times, and finish with a fourth and final layer of kohlrabi slices.

Squeeze the lemon juice into the milk pan, then pour this over the kohlrabi. Place on a baking tray (in case the cream bubbles over) and cook in the middle of the oven for 45-50 mins, until the kohlrabi and leaves have released their juices and become tender.

The cream should be bubbling round the sides and brown on top.