Slice the croissant in half horizontally and open both sides. Spread a little mayo and mustard on the top and bottom of the croissant.
Place the lettuce leaves on both halves of the croissant and layer your ingredients so that the cheese, salami, and slices cherry tomatoes are between the two lettuce leaves. Close the sandwich.
Pack it for lunch:
Slice the croissant sandwich in half and place it inside a lunch container where it fits snugly, so everything stays in place.
Pack any sides, like fruits and veggies, in a separate compartment or container. Refrigerate until ready to pack inside a lunch bag, with or without an ice pack.