Rosti fish cakes

Thickly grate the potatoes onto a plate, then squeeze handfuls of it to remove any excess liquid. Put it in a large bowl, then add the tuna, capers, spring onion and beaten egg, and season well with ground black pepper.

Heat half the olive oil in a large frying pan. Divide the potato mixture into 4 and spoon into the pan in mounds, gently pressing down with the back of a spoon. You may have to do this in batches. Cook for 7-10 mins, turning once, until crisp and golden.

Put the asparagus in a frying pan and cover with boiling water from the kettle. Bring to the boil and cook for 3 mins or until the asparagus is just tender, then drain. Mix the remaining oil with the lemon juice and mustard and season well. Put the watercress in a bowl and drizzle over the oil and lemon juice mixture. Toss well. Serve the fish cakes with the asparagus and watercress.