Step 1

Pull the soft centre out of each roll and place in a food processor. Whiz to fine breadcrumbs, then add the mince, parsley, parmesan, chilli flakes, garlic and Worcestershire sauce. Pulse to combine, and season, then add the egg. Pulse until the mixture just comes together.

Step 2

Using damp hands, form mixture into 16 walnut-sized balls and place on a lined baking tray. Chill for 15 minutes to firm up.

Step 3

Heat the olive oil in a non-stick frypan over medium heat. Add the meatballs and cook, turning, for 6-8 minutes until golden and cooked through. Add the passata and bring to a simmer, then reduce the heat to low and cook for a further 6-8 minutes until the sauce has thickened and reduced.

Step 4

Preheat grill to high. Place the rolls on a lined baking tray. Fill each roll with 4 meatballs and some tomato sauce, then top with gruyere. Grill for 1 minute or until the cheese starts to melt, then serve.