Cook the potatoes in a saucepan of lightly salted boiling water for 10 minutes, then remove from
the heat, cover and stand for 15-20 minutes or until tender.
Meanwhile, slice the egg, then cut each slice in half. Whisk the olive oil and vinegar together
in a bowl and season to taste with salt and pepper. Spoon a little of the vinaigrette into a
serving dish to coat the base.
Drain the potatoes, then peel and thinly slice. Place half the slices over the base of the dish
and season to taste with salt, then top with half the tuna, half the egg slices and half the
shallots. Pour over half the remaining dressing. Make a second layer with the remaining potato
slices, tuna, egg and shallots, then pour over the remaining dressing.
Finally, top the salad with the tomato and parsley. Cover with clingfilm and stand in a cool
place for 1-2 hours before serving.