This is a sure-fire and colorful way to use up that leftover chicken. If you don’t have pesto, use regular mayo. I always drizzle the chicken with a tiny bit of oil and vinegar for a little added zip.
Preheat your broiler to high. Cut four 3-inch slices from the ciabatta loaf. Cut each piece in half lengthwise and brush both sides with olive oil.
Place the pieces on a sheet pan and toast each side lightly under the broiler, being careful not to burn the bread. Remove the sheet pan from the oven. In a small stainless steel bowl, mix the mayonnaise and the pesto. Slather the inside of the bread slices with the pesto mayonnaise or regular mayonnaise. Divide the cheese evenly between each slice of bread and return the sheet pan to the broiler until the cheese is just melted.
Assemble the sandwiches by stacking the chicken, roasted red pepper, and shredded lettuce on a slice of the toasted bread. Add salt and pepper to taste and drizzle the lettuce with olive oil and vinegar. Top with the remaining slice of bread, cut in half, and serve with a green salad.