In a food processor bowl, place the mince, onion, garlic, 2 teaspoons chilli flakes, tomato paste, breadcrumbs and thyme and process until combined.
Line 2 baking trays with baking paper. Slice sheets of pastry in half and remove plastic backing.
Evenly distribute the mince mixture amongst the pastry sheets and form a thin sausage shape. Roll the pastry sides to a close, over lapping underneath.
Brush sausage rolls with a small amount of milk and top with remaining chilli flakes.