- In a small non-stick skillet over medium-low heat, soften the onion in the oil until nicely golden, stirring often. Let cool.
- In a large pot, bring the broth, Parmesan rind and one rosemary sprig to a boil. Simmer for 15 minutes. Season with salt and pepper. Remove and compost the Parmesan rind and rosemary sprig.
- Meanwhile, in a bowl, combine the sausage meat, grated Parmesan and cooled caramelized onion. Mix well.
- On a work surface, lay out 4 wonton wrappers. Place 1 tsp of the sausage filling at the centre of each wrapper. Using a pastry brush, wet two adjacent sides of each wrapper with water and fold over towards the opposite sides to form a triangle. Press together to seal around the filling. Moisten one of the two remaining tips and pinch together with the opposite tip to seal. Place the tortellini on a baking sheet as you go and cover with a dishcloth to prevent from drying out. Repeat with the remaining wrappers and filling.
- Cook the tortellini in the simmering broth for 5 minutes. Break the remaining rosemary sprig into small bouquets.
- Serve the tortellini and broth in bowls. Top each bowl with a rosemary bouquet and grated Parmesan. Season with pepper.