Provençal picnic sandwich (Pan bagnat)

This is a speciality of Nice and is filled with Niçoise salad ingredients. A great way to use up slightly stale bread, the recipe contains tuna and anchovies but if you are vegetarian, you could substitute with cheese (such as mozzarella or slices of goats’ cheese) or roasted peppers, aubergines, courgettes and mushrooms. Make this a day ahead and keep weighted down in the fridge so all the juices seep into the bread.