To assemble: Spread each crostini with caramelised onion relish, followed by mozzarella, prosciutto and a basil leaf. Sprinkle with some chilli flakes (if desired) and drizzle with balsamic glaze. Season well and serve immediately.
0.25 cup caramelised onion relish, 200 g fresh mozzarella cheese, 100 g prosciutto, 25 basil leaves, chilli flakes, 2 tbsp balsamic glaze