Slice each toasted slice of rye bread into 4 fingers, then cut in half to make 32 in total. Arrange over boards or platters for serving.
Drain the peas well, then tip into a bowl with the crème fraîche, mint sauce, lemon juice and plenty of freshly ground black pepper. Use a potato masher or fork to mash everything together to a rough crush (or pulse in a food processor for speed).
To serve, spread a little of the crushed pea over each rye finger, top with a ruffle of salmon and snip over the cress.