Taught to me by my mother-in-law and completely foolproof. Take the salmon, whether a piece or the whole fish, and let it lie flat in a pan in which it fits neatly (for a whole fish, you’ll need a fish kettle). Add cold water until the salmon is just submerged, then a pinch of salt and, if you like, a glug of olive oil and white wine. Put the pan on a hot gas or electric or Aga hotplate until the water reaches a gentle boil.
Remove the pan and leave the fish to cool. By this time, it will be cooked. The magic is that the length of time it takes to reach the boil and then cool is in proportion to the weight of the fish. Serve, of course, with tiny, peeled new potatoes, a cucumber salad (I like just a spray of white-wine vinegar, no oil) with chopped chives and homemade mayonnaise. Not chic, not trendy, a cliché but delicious.