Pastitsio with mortadella zenah

Ingredients

• 1 tablespoon mustard
• 1 tablespoon sweet mayonnaise
• ½ tablespoon balsamic vinegar
• 1 teaspoon oregano
• 1 teaspoon salt
• 3 tablespoons lemon or orange juice
• 380g Mortadella zenah, diced
• 180g lettuce, chopped into small pieces
• Toasted bread cubes