Bring a pan of salted water to a boil and tip in the green beans. Cook for 2-3 mins until tender but with a bite, then drain and plunge into ice-cold water. Leave for 5 mins before draining and drying thoroughly.

Spread the softened butter over the cut sides of the bagels. In a bowl, combine the mustard, mayonnaise and cornichons with a good grind of black pepper. Spread this over the butter.

Separate the lettuce leaves from the head of lettuce, then wash and dry thoroughly. Layer 2-3 lettuce leaves over the base of the bagel. Layer up the green beans, ham, olives and cheese and top with the other half of the bagel. Wrap well in baking parchment to take with you.