The tuna melt is one of those gloriously unfussy sandwiches that doesn't need much convincing. Tuna, mayonnaise, crisp celery, tomato and an unreasonable amount of melted cheese, all tucked between toasted bread. My version has one slightly geeky trick: emulsifying extra virgin olive oil into the tuna, which makes the filling remarkably creamy and gives it a grassy, slightly bitter richness. It is part sandwich, part diner nostalgia, and basically a hot, cheesy hug you will absolutely not regret.