Forshmak

Check the herring fillets over with your fingertips and pull out any pin bones you find.

Lay them in a dish, pour over 250ml of the milk and refrigerate for 2 hours.

Soaking is not optional and the timing is not fixed. Shop-bought salt herring ranges from mildly cured to brutally salty, and a batch made without soaking can be genuinely inedible.

Taste a corner of a fillet after 2 hours. It should be pleasantly salty rather than harsh; if it still stings, change the milk and give it another hour.

Lower the eggs into a pan of boiling water and cook at a bare simmer for 9 minutes.

Lift them straight into cold water, then peel them once cool.

Tear the stale bread into the remaining 50ml of milk and leave it for 5 minutes, then squeeze it out in your fist.

Drain the herring, pat the fillets dry and cut them into rough pieces.

Chop the apple, onion and two of the eggs roughly, and pile them onto a large board with the herring and the squeezed bread.

Work through the pile with a heavy knife, sweeping it back together and chopping again, for 5-8 minutes, until you have an even coarse paste with no piece bigger than a grain of rice.

Chop it, do not blitz it. A food processor turns forshmak into a smooth pink puree within seconds, and the slightly rough texture is most of what the dish is.

Beat the softened butter in a bowl for a minute, until creamy and pale.

Work the chopped mixture into the butter in three additions.

Season with the mustard, lemon juice, sugar and ground peppercorns.

Taste before you consider salt. The herring is bringing all the salt there is going to be, and it is easy to be caught out.

Fold in half the dill.

Cover and refrigerate for 1 hour, which firms the butter and lets the flavours settle into each other.

Grate the remaining egg over the top through the coarse side of a box grater.

Scatter the rest of the dill over.

Serve cold, spread thickly on dark rye bread.

Keep it refrigerated and eat it within two days.