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Smoked Mackerel & Leek Gratin

Smoked Mackerel & Leek Gratin

4rating out of 5

(462 reviews from our customers)

Prep Time

45 min



We’ve added a twist to this classic cheesy gratin by using grated potatoes rather than sliced. This makes it quicker and binds the potatoes and cheese sauce together. Rich smoked mackerel seasons the dish and adds a savoury depth. Served with a punchy Dijon and white wine vinegar dressed little gem side-salad for balance. Grate stuff!

Prep Time

45 min



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What is Gousto all about?

We send you everything you need to cook amazing recipes like this, delivered right to your door. Leave the planning to us!

For 2 people (double for 4)
1 leek
1 little gem lettuce
2 garlic cloves
10g fresh chives
1 tsp French Dijon mustard †
40g Irish mature cheddar †
Panko breadcrumbs edit
30g panko breadcrumbs †
300g potatoes
1 dried bay leaf
1 tbsp white wine vinegar
100g British smoked mackerel fillet †
You Will Need
Butter, flour, milk, olive oil, pepper, salt

Nutritional Information*

Percentages are based on an adult's daily intake

  • 1 leek
  • 1 little gem lettuce
  • 1 garlic clove
  • 10g chives
  • 1 tsp Dijon mustard<span class="strong">†</span>
  • 40g cheddar cheese<span class="strong">†</span>
  • 30g panko breadcrumbs<span class="strong">†</span>
  • 300g potatoes
  • dried bay leaves
  • 1 white wine vinegar sachet (15ml)
  • 1 x 100g British smoked mackerel fillet<span class="strong">†</span>
Typical Values per 100g per serving
Energy 372 kJ
88 kcal
1838 kJ
437 kcal
of which saturates
3.3 g
1.4 g
16.3 g
7.1 g
of which sugars
10.5 g
1.8 g
52 g
9.1 g
Fibre 1.8 g 9.1 g
Protein 5.1 g 25.1 g
Salt 0.34 g 1.68 g
*Gousto’s nutritional information only applies to ingredients supplied by Gousto. The cooking process and additional ingredients added at home (listed under “What you’ll need”) will affect total values.
Ingredients contain
1 leek
1 little gem lettuce
little gem lettuce
1 garlic clove
10g chives
chives (100%)
1 tsp Dijon mustard
water, mustard seeds, spirit vinegar, salt, potassium metabisulphite (sulphites), citric acid
40g cheddar cheese
pasteurised cows milk, cream, salt, vegetarian rennet, lactic acid culture
30g panko breadcrumbs
wheat flour (gluten), sugar, salt, yeast
300g potatoes
dried bay leaves
dried bay leaves
1 white wine vinegar sachet (15ml)
white wine vinegar
1 x 100g British smoked mackerel fillet
mackerel (fish) (97%), salt
  • Allergens highlighted by † (mustard, sulphites, milk, gluten, fish)

In addition to the recipe specific allergen information provided, due to production and packing methods Gousto boxes may also contain low levels of the following allergens: Cereals containing gluten; Crustaceans; Eggs; Fish; Peanuts; Soya; Milk; Nuts: almonds, hazelnuts, walnuts, cashews ,pecan nuts ,brazil nuts, pistachio nuts, macadamia nuts; Celery; Sesame; Sulphur dioxide and Sulphites; Lupin; Molluscs; Mustard.

Cooking Instructions
Instructions for 2 people (double for 4)
1 Smoked Mackerel & Leek Gratin

Preheat the oven to 220°C/ 200°C (fan)/ 425°F/ Gas 7

Boil a kettle 

Grate the potatoes (skin on) 

2 Smoked Mackerel & Leek Gratin

Add the grated potato to a pot of boiling water and bring to the boil over a high heat with a pinch of salt

Once boiling, cook the potato for 5 min, then drain and leave to steam-dry in a sieve 

3 Smoked Mackerel & Leek Gratin

Meanwhile, slice the leek[s] finely

Heat a large, wide-based pan (preferably non-stick) with 40g [80g] butter and a drizzle of olive oil

Once melted, add the leeks and cook for 3 min or until starting to soften

4 Smoked Mackerel & Leek Gratin

Add 1 tbsp [2 tbsp] flour to the softened leeks and cook for 1 min, stirring it with a wooden spoon

Add 300ml [600ml] milk and whisk for 3-5 min into a smooth sauce 

Meanwhile, peel and grate the garlic into the sauce and add the bay leaf

5 Smoked Mackerel & Leek Gratin

Remove the skin from the mackerel and discard it, then break the mackerel up into different sized pieces, some small flakes and some larger chunks

Grate the cheddar

Once thickened, remove the sauce from the heat, and mix in the drained potato, mackerel and cheddar with a pinch of salt and pepper 

6 Smoked Mackerel & Leek Gratin

Remove the bay leaf and transfer the mixture to an oven-proof dish (or individual ones) 

Scatter the panko breadcrumbs over 

Put the gratin[s] on a baking tray and into the oven for 10 min or until bubbling and golden on top  

7 Smoked Mackerel & Leek Gratin

Tear the little gems roughly and add them to a bowl to serve

Chop the chives finely

For the dressing, combine the mustard, white wine vinegar, chives and 2 tbsp [4 tbsp] olive oil with salt and pepper

Dress the salad just before serving 


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Once golden, serve the gratin with the salad to the side (it will be very hot!)


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