There are tiny blue mussels on the fishmonger’s slab, their shells shut tight, glistening among the hills and valleys of crushed ice. I buy 1kg. Half will be steamed and shelled, their orange and ivory flesh tossed with crisp shavings of fennel and segments of something citrus; the others will be baked in a vegetable-crusted pie with smoked fish and tarragon.

I am ruthless when it comes to cleaning mussels

I am not the most meticulous of cooks, but I am ruthless when it comes to cleaning mussels. They clatter into the sink then get an inspection worthy of CSI. Each one is checked for signs of vibrant life, by which I mean tightly clamped shells or, if they are open, hinges that snap shut swiftly when tapped on the side of the sink. Any pesky wisps of beard are tugged from the closed shells and anything broken or cracked gets the heave-ho.

Casting session over, the mussels are thoroughly washed in freezing water and hastily thrown into a deep pan and steamed for a minute or two until their shells open. The temptation to serve them as they are is almost irresistible, perhaps with nothing more than a pot of butter-yellow garlic mayonnaise and some crisp-crusted bread. But I resist, there is more than just myself to feed. I want salad and they want pie.

Leek, smoked haddock and mussel pie

You could use potatoes, blanched for 5 minutes, in place of the celeriac.

Serves 4

smoked haddock fillet 350g

milk 500ml

water 100ml

bay leaves 3

black peppercorns 6

mussels 500g

leeks 2, large (600g)

butter 90g

tarragon 5 stems

plain flour 2 tbsp

celeriac 700g

Put the fish in a pan, pour in the milk and water, bay leaves and peppercorns and bring to the boil. Remove from the heat, cover with a lid and leave for 20 minutes.

Wash, check and remove the beards of the mussels as before, then tip them into a deep pan with a wine glass of water and bring to the boil. Cover with a lid and cook for 2 or 3 minutes until the shells have opened. Remove from the heat, pull out the mussels from their shells and discard the shells. Strain the liquor into the haddock pan.

Discard the thick, dark green part of the leeks. Cut the leeks into pencil-thick rounds and rinse in cold water. Melt 50g of the butter in the empty mussel pan, add the leeks and cook on a low heat for 10 minutes or so, turning regularly so they do not brown. Remove the haddock from the pan and break into large flakes, discarding the skin as you go. Remove the leaves from the tarragon, discard the stems and roughly chop the leaves.

Stir the flour into the leeks and cook for 2 minutes. Ladle in 300ml of the liquid from the haddock pan. Mix well and leave to cook for 5 minutes over a low heat, stirring regularly. Gently fold the haddock, mussels and tarragon into the leeks and season with salt and black pepper, then transfer to a 24cm pie dish. Set the oven at 200C/gas mark 6.

Peel the celeriac and cut into slices no thicker than a £1 coin. Cut discs from the slices using a 5cm round cutter (save trimmings for the stockpot). Melt the remaining butter in a small pan, season with black pepper then add the discs of celeriac and toss to coat in the butter. Place the celeriac on top of the pie and bake for 45 minutes or until golden.

A salad of mussels and grapefruit

Curiously appealing: salad of mussels and grapefruit. Photograph: Jonathan Lovekin/The Observer

There is something curiously appealing about a refreshing salad on a cold day. The crispness of fennel, the citrus notes of grapefruit and the clean, aniseed notes of fresh dill contrast with the rest of the carb-heavy winter offerings.

Serves 3

mussels 500g

pink grapefruit 2, chilled

fennel 1 bulb

cucumber half a large one

parsley leaves a handful

dill fronds a handful



For the dressing:

reserved grapefruit juice 3 tbsp

olive oil 5 tbsp

small capers 2 tsp

Wash, check and remove the beards of the mussels. Tip the mussels into a large, deep pan. Pour in a cupful of water and place over a high heat, cover the pan with a tightly fitting lid. Bring to the boil then leave to steam for 2 or 3 minutes until the shells have opened. Remove from the heat, leaving them in the pan.

The crispness of the fennel and the citrus notes of grapefruit are a contrast to many winter offerings

Remove the skin from the grapefruit with a sharp knife then remove the segments, saving as much juice as possible. Cut the fennel in half from tip to base and then into paper-thin slices and add to the grapefruit, tossing the fennel with the grapefruit juice to prevent it discolouring.

Peel the cucumber, cut it in half lengthways then remove the seeds and core with a teaspoon. Cut into 1cm thick pieces and add to the grapefruit.

Pull the parsley leaves from their stalks, add to the salad then roughly chop the dill and fold that in, too.

In a small bowl mix together 3 tbsp of the reserved grapefruit juice (you can drink the rest), the olive oil, a grinding of salt and black pepper and the capers. Remove the mussels from their shells and add them to the dressing, then fold through the fennel and grapefruit, and serve.

The Observer aims to publish recipes for fish rated as sustainable by the Marine Conservation Society’s Good Fish Guide

Email Nigel at nigel.slater@observer.co.uk or follow him on Twitter @NigelSlater