The haddock are headed, cleaned, split open (but not de-boned) and soaked in 175 F (80 C) brine for 7 to 15 minutes, depending on the fish size.
They are then cold-smoked at 75 to 80 F (24 to 27 C) over a fire made from oak sawdust, from 3 to 6 hours, depending on the size of the fish.
The flesh comes out a colour like that of a pale lemon.
The fish may be sold with tail and fins still on, or cut off. You can also buy fillets canned.
They are usually just referred to as “Finnans.”
Eyemouth Pales (from the Borders) are similar, though they are smoked for less time. They also have the bones still in them. Their colour is paler, more like a straw.
These are different from Arbroath Smokies, which are hot smoked and so don’t need cooking.
Despite the processing, treat Finnan Haddock as raw and in need of cooking. It is often cooked by poaching it in milk.
To poach it in milk, place it in a saucepan with about 1/2 inch (1 cm) of milk, and a tidge of butter. Bring to a boil, then reduce heat and from that point allow to simmer about 4 minutes. To be fancier, you can use white vermouth or wine instead of milk.
Some people thicken the milk with cornstarch or flour, making a sauce, and put the cooked fish on toast and pour the sauce over it all.
You can also bake them or cook them under the broiler (aka grill in the UK.)
Literature & Lore
“Any dried or smoked fish can be cooked the way they prepare Finnan haddies in Aberdeen. Grease the bars of your grill, place the fish on it, skin upwards, and grill slightly to prevent fish curling when turned, place a heaped teaspoon butter on each Finnan, and finish grilling under a slower heat than usually required for grilling till quite cooked. Do not turn on the other side again. If dried up, melt a pat of butter on top of each fish and serve with or without a poached egg on top. Enough for four persons.” — Elizabeth Craig. “Highlands of Scotland Give Smoked Fish Recipes.” Reprinted in: Syracuse Herald, New York State. 16 May 1926, Home Institute Page.