Preheat oven to 200℃ (180℃ fan forced) and line a baking tray with baking paper.
In a large bowl combine pork mince, French onion soup mix, thickened cream, caramelised onions, parsley, mustard, garlic, breadcrumbs, egg and pepper, to taste. Mix until well combined.
Cut each sheet of puff pastry in half to create six long strips.
Divide the filling into six equal portions. Shape each portion into a long log along one edge of each pastry strip.
Brush the opposite edge with egg wash, then roll the pastry over the filling to enclose.
Place seam side down and cut each roll into four pieces.
Arrange sausage rolls on the tray. Brush the tops with egg yolk and sprinkle with your preferred topping.
Bake for 25 to 30 minutes until golden and cooked through. Allow to rest for a few minutes before serving with your preferred dipping sauce.