Cook the broccoli florets in a saucepan of lightly salted boiling water for 3 minutes. Drain, rinse with cold water and chop into small pieces. Make up the mash according to the packet instructions, add the Parmesan and mix well.
Place the salmon on a microwave-proof plate and cover with clingfilm. Cook for 2–3 minutes until the fish is opaque.
Mix the potato with the broccoli and salmon, then divide into 4 pieces. Shape into patties, using metal spoons if the mixture is too hot to handle. Put the flour on one plate, the beaten egg on another and the breadcrumbs on a third. Lightly roll the fishcakes in the flour, then the egg and finally the breadcrumbs.
Heat the oil in a large heavy-based frying pan and cook the fishcakes for 2–3 minutes on each side. Drain on kitchen paper and serve with peas and sweetcorn, if liked.