1. Turn each roll on its side and, using a serrated knife, slice the top off. Set aside to use as lids.
2. Using a teaspoon, pull the soft bread out of the remaining rolls, keeping the crust only. (Instead of discarding the soft bread, blitz to make breadcrumbs – freeze and use another time.)
3. For the slaw, thinly slice the fennel, then chop it and mix it in a bowl with the yogurt, pesto and basil leaves. Set aside.
4. Put 3 slices of salami inside each roll to form a base. Tear half of the cheese slices into pieces and place over the salami, pressing down to make as much room as possible inside the rolls. Next, add a layer of tomato, followed by a layer of slaw. Tear the remaining cheese into pieces and put a final layer in each roll. Top with the lids.
5. Cut each roll in half using a serrated knife, then tightly wrap each roll in foil and pack in a cool box to take on your picnic.
TIP: Substitute ham or prosciutto for the salami if you prefer. Or make the rolls vegetarian by leaving out the salami.