The secret to this delicately crafted sandwich lies in the arrangement of the vegetables in thin, even layers. Given that the recipe includes a rather intense spread, you can grill the veggies without the need to marinate them. Opt for a ciabatta bread because it's robust enough to hold all the ingredients without making it too difficult to eat. Grill it on one side only for a wonderfully toasted flavour, and also to keep the veggies from getting soggy.