Add the crab, potato, onions, 125 ml flour, lemon juice, eggs and pepper to a mixing bowl.
Stir well to combine.
Place remaining flour in a separate bowl or plate.
Shape mixture into 8 round patties, then coat with a mixture of remaining flour and sesame seeds.
Heat oil in a frying pan and fry the fishcakes for 10 min, turning once, or until golden brown.
Pour KNORR Classic White Sauce sachet contents into a measuring jug and fill up to the 250 ml mark with boiling water.
Add the lemon juice and butter and stir well with a fork for 1 minute until thick.
Stir in chives.
Serve the fish cakes with sauce and a crisp green salad.