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Celeriac and smoked mackerel gratin

Name: Celeriac and smoked mackerel gratin
Prep time: 25 min
Cook time: PT40-45M
Total time: 1 h 5 min
Yield: Serves 3-4
Ingredients: Knob of unsalted butter; 2 onions, sliced; 4 thyme sprigs, leaves picked; 2 garlic cloves, sliced; 200g whole milk; 200g double cream; 1 tbsp wholegrain mustard; 1 bay leaf; 1 medium (450g) celeriac, scrubbed clean or peeled; 2 peppered smoked mackerel fillets; 1 tbsp fresh or panko breadcrumbs; 1 tbsp hazelnuts, roughly chopped; 30g comté cheese, grated (optional); Rocket salad to serve (optional); Specialist kit; Mandoline (optional)

By: Pollyanna Coupland
Food producer, delicious.

Published: 20 Feb 23
Updated: 18 Mar 24

Peppery smoked mackerel and sweet, earthy celeriac get the gratin treatment to create something rich, indulgent but super simple to prepare. Serve with a crisp and peppery rocket salad to cut through the rich gratin.

Have you seen Marcus Wareing’s incredible celeriac and tahini potato gratin?

Easy
March 2023

Test kitchen approved

Serves 3-4
Hands-on time 25 min. Oven time 40-45 min

Have you seen Marcus Wareing’s incredible celeriac and tahini potato gratin?

Freezable

Nutrition: Per serving (for 4)

Calories: 585kcals
Fat: 48.8g (23.5g saturated)
Protein: 18.4g
Carbohydrates: 14.35g (9.9g sugars)
Fibre: 7.7g
Salt: 1.6g

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Ingredients

Knob of unsalted butter
2 onions, sliced
4 thyme sprigs, leaves picked
2 garlic cloves, sliced
200g whole milk
200g double cream
1 tbsp wholegrain mustard
1 bay leaf
1 medium (450g) celeriac, scrubbed clean or peeled
2 peppered smoked mackerel fillets
1 tbsp fresh or panko breadcrumbs
1 tbsp hazelnuts, roughly chopped
30g comté cheese, grated (optional)
Rocket salad to serve (optional)

Specialist kit

Mandoline (optional)

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Method

Melt the butter in a frying pan then add the onions and garlic and cook for 12 15 minutes until soft and caramelised. Meanwhile, put the milk, cream, mustard, bay leaf and a pinch of salt and pepper in a saucepan and bring to the boil, then set aside to infuse
Finely slice the celeriac, using a mandoline if you have one. Spoon some of the onions into the bottom of a medium baking dish and flake in some of the mackerel, then cover with a layer of celeriac. Repeat until all the ingredients are used up, finishing with a celeriac layer. Pour over the cream mixture (discarding the bay leaf), then sprinkle over the breadcrumbs, hazelnuts and cheese (if using).
Cover the dish with foil and bake in the oven at 160ºC fan/gas 4 for 45–60 minutes (the time will depend on how finely you sliced the celeriac) until a knife can go through the gratin with little resistance. Remove the foil for the last 5 minutes to get a golden bubbly topping. Serve with the salad on the side.