Prep the ingredients
Peel and thinly slice the onion. Pick the leaves from the parsley, rinse them well, shake them dry, and finely chop enough to give you about 30 g. Rinse the eel pieces under cold running water and pat them dry; if you are starting with a whole eel, have your fishmonger clean, skin, and cut it into 3–4 cm pieces with the bone in, since that is much easier and safer with the proper tools.
Simmer the eel
Put the eel into a roomy saucepan and pour in the cold water so it just covers the pieces. Add the sliced onion, bay leaf, black peppercorns, malt vinegar, fine salt, and a pinch of white pepper if you want a little extra warmth. Bring everything slowly to a simmer over medium heat, skimming off any foam from the surface, then keep it at a very gentle simmer; a hard boil will break up the eel and cloud the jelly. Cook for 25–30 minutes, until the eel is tender but still holding its shape and the liquor tastes well seasoned.
Set the jelly
Lift the eel pieces out with a slotted spoon and arrange them in a shallow serving dish or in individual bowls, removing any obvious loose bits of skin or stray bone as you go. Strain the cooking liquor over the eel, leaving the onion, bay leaf, and peppercorns behind. Let it cool at room temperature for 20 minutes, then cover and chill for 3 hours, or until the stock is clear and softly set around the fish.
Make parsley sauce
When the eel is nearly set, melt the unsalted butter in a small saucepan over medium-low heat. Stir in the plain flour and cook the paste for 1–2 minutes without letting it brown, then gradually whisk in the whole milk a little at a time until smooth. Bring to a gentle simmer and cook for 5–8 minutes, whisking now and then, until the sauce lightly coats the back of a spoon. Stir in the chopped parsley, add a pinch of ground nutmeg if you like, and season with salt and more white pepper to taste.
Serve
Spoon the warm parsley sauce alongside the chilled jellied eels, rather than over the top, so the jelly keeps its shape. Offer extra malt vinegar at the table for anyone who likes a sharper finish.


















