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Mackerel Sauce, or Fennel Sauce
Pick fennel from the stalks, and boil it for a minute or two in boiling salted water, then chop it fine. Mix and blend well two dessert-spoonfuls of baked flour with nearly a quarter of a pound of butter, put it into a saucepan with half a pint of boiling water, and stir until thick, add two dessert-spoonfuls of fennel, and serve hot in a tureen. Mackerel roes (soft ones) boiled and bruised well with yolk of hard-boiled egg may be added to the sauce, stirred in with the fennel. Time, ten minutes to simmer butter. Sufficient for a tureen.
A butter-and-flour sauce of the old English school, built for oily grilled or boiled mackerel. It is essentially a loose roux thinned with water rather than milk, so the fennel and the fish fat carry the flavour.
- Baked flourPlain flour dried in a low oven until it just begins to colour, then cooled and sieved. It thickens without the raw, pasty taste of untoasted flour; a blond roux cooked a few minutes achieves the same thing.
- Dessert-spoonfulTwo teaspoons, or roughly 10 ml. Two dessert-spoonfuls of flour is only about 10 g, which against nearly 110 g of butter gives a very loose, buttery sauce rather than a set one.
- Imperial half-pintThis is a British book, so half a pint is 10 fl oz, about 1¼ US cups. Using a US half-pint will leave the sauce noticeably heavier.
- Which fennelThe herb, not the bulb vegetable: the feathery green fronds of Foeniculum vulgare, picked from the stalks. Bronze fennel or the tops of a Florence fennel bulb both work. Dill is a common modern substitute.
- Blanching the frondsA minute in salted boiling water sets the colour and takes the raw edge off. Refreshing in cold water and squeezing dry before chopping will stop the fennel thinning the sauce.
- Soft roesThe milt of the male mackerel, sold as soft roe or laitance where fishmongers still bother with it. Poach gently until firm, then mash with hard-boiled yolk; it turns the sauce into something closer to a rich, savoury dressing.
- The ten minutes"Time, ten minutes to simmer butter" means the butter and flour base, not the finished sauce. Add the fennel at the very end and serve at once — held hot, the herb loses its scent and the butter separates.
- YieldThe recipe specifies only "sufficient for a tureen."
Fennel with mackerel is often said to be a long-standing traditional pairing in English cookery. The logic is straightforward — mackerel is an intensely oily fish that spoils faster than almost anything else landed in Britain, and the anise sharpness of fennel cuts the fat while the sauce's butter keeps the flesh from tasting dry. The addition of soft roes — the milt of the fish — folds part of a cheap fish back into its own sauce.