200 g (7 oz) Swiss cheese, such as Emmental or Gruyère, grated
1 tablespoon wholegrain mustard
2 tablespoons mayonnaise
2 tomatoes, deseeded and chopped
pinch of black pepper
1 round lettuce, to serve (optional)
Cut the French stick in half, then slice each half horizontally to form 4 long pieces.
Place the grated cheese in a bowl with the remaining ingredients and mix well to combine.
Spoon the topping over the cut side of each piece of bread and place on a baking sheet. Cook under a preheated hot grill for 3–4 minutes, until golden and bubbling. Serve hot with lettuce leaves, if desired.