They may not sound like a natural pairing, but mango and mozzarella, like tomatoes and mozzarella, work remarkably well together. Don't be intimidated by the cardamom syrup. It's easy to make and tastes great on the savory-sweet salad.
Make the syrup: Bring Lillet, vinegar, and honey to a simmer in a small saucepan over medium heat. Remove from heat, and add cardamom pods. Let stand, covered, until completely cooled. Strain syrup through a fine sieve; discard solids.
Meanwhile, make the croutons: Heat oil in a medium saucepan over medium heat until it reaches 350 degrees on a deep-fry thermometer. Fry bread, stirring occasionally, until golden brown, about 4 minutes; transfer to paper-towel-lined plates using a slotted spoon. Let croutons drain. Sprinkle with salt.
Make the salad: Divide frisee evenly among 4 plates. Top with half the cheese, then half the mangoes. Repeat with remaining cheese and mango. Layer onion, blackberries, and then croutons on top.
Drizzle 1/4 cup cardamom syrup over tops, allowing it to pool at the bottom. Season with salt and pepper.