02Cut the bread pieces horizontally in half. Grill the bread cut-side down on a grill pan over medium-high heat until golden, about 2 minutes. Rub the whole garlic cloves over the toasted side of the bread. Add a slice of mozzarella to bread bottom, spoon the caponata on top, cover with the other bread half, and serve.03To take for a picnic: Wrap the sandwiches separately in plastic wrap or parchment paper. Chill until ready to serve, or keep at room temperature up to 1 hour.