Add the diced potatoes to a pan of boiling water; put the salmon fillets in a metal colander and sit it directly over the pan to steam above the potatoes; put the lid on top of the fish; the fish will take about 10 minutes to cook and the potatoes about 15 minutes
Remove the fish when it’s ready and leave to cool; drain the potatoes and mash; add the lime zest, ginger, coriander and seasoning and mix well together; break the salmon into chunky flakes, then mix gently into the mashed potato; leave to cool a little
Divide the fish mixture into 5, roll into balls, then flatten slightly; dust with flour then carefully shallow fry in the oil for 3-4 minutes each side
Split the focaccia in half; lightly toast it and spread the lower half with the tartare sauce if using; place some shredded lettuce and tomato slices on top followed by a salmon burger and the top half of the focaccia and serve
5 servings