Whoa, steady on! This is rich, as in old-fashioned Frenchified rich, dripping with cream. It’s the sort of thing you should treat yourself to once a winter.
Serve with a mass of tangy salad leaves, or a mound of broccoli or broccolini. The broccoli won’t need any dressing, as there’ll be a nice little puddle of creamy sauce to pass it through on your plate, but it’s crunch will make a nice contrast. This is a complete meal and is good with any wine with a bit of bite or acidity. Make it on a nippy day when you are hanging out for something decadently creamy and satisfying, something to warm you up right down to your boots.
1 large onion, peeled and finely sliced
1 Tbsp butter
1 small celeriac, about 500g (about 1 pound)
Juice of 1 lemon
500g (about 1 pound) medium potatoes
250g (8-9 ounces) hot-smoked salmon
¼ cup chopped dill
Flaky sea salt, freshly white pepper
300ml (10 fluid ounces) double (heavy) cream
1 Preheat oven 200°C (400°F). Put the onion and butter in a small frying pan (skillet) and cook gently until softened and lightly golden; stir often.
2 Peel celeriac with a sharp sturdy knife, ensuring all deep roots are removed (keep chopped board clean from any dirt while preparing celeriac). Cut into chunks, then slice thinly, and as it is prepared, put it in a bowl of water with lemon juice to slow discolouration. When all the celeriac has been prepared, drain and transfer to a saucepan, cover with cold water and a few squirts of lemon and bring to the boil. Lower heat and cook for 3 minutes, drain.
3 Peel and slice potatoes thinly with a sharp knife or using a mandolin. Remove skin from salmon and pat with paper towels to remove excess oil. Flake into large pieces.
4 When celeriac is cool enough to handle, layer in a dish with potatoes, onion, salmon and dill. Season the potatoes and celeriac as you go. Make three layers of potato, celeriac and onion, and two of salmon, but finish the top with sliced potato, not celeriac. (I use an ovenproof china dish 24cm wide by 6cm deep – about 9½” wide by 2½” deep.)
5 Spoon the cream over the top of potatoes. Cover dish with foil and place it in a shallow roasting tin or on a baking tray in case of spills. Bake for 45 minutes, then remove foil and continue cooking for about 30 minutes, or until bubbling and golden on top and the vegetables are tender. Rest the gratin for 10 minutes before serving.