Heat the oven to 180°C. Bake the hazelnuts on a baking tray for 10 minutes. Leave to cool and chop, in a large bowl, combine the sliced courgettes, olive oil, vinegar, herbs, chilli and crushed garlic. Cover and set aside.
Heat the butter in a frying pan on a gentle heat and fry the onions with the sugar until caramelised, add the shredded radicchio for 1-2 minutes, then remove and set aside
Cut the tip off the garlic clove and lightly rub one side of the bread, then drizzle them with a little oil preheat a char-grill pan and Toast the bread until marked and nicely grilled turning once.
Add the onion and radicchio mix into the courgette mixture. Arrange on a platter, chuck on the hazelnuts, mozzarella and extra mint, then serve with the grilled toast.