Cut two thawed sheets of frozen puff pastry in half. Spread each half with 2 teaspoons dijon mustard, leaving a 2cm border.
Place 1 ½ of your favourite sausages along long edge of each piece of pastry. Roll to enclose and brush with a lightly beaten egg.
Cut each roll into 3cm slices and place on a baking tray lined with baking paper. Cook for 20 minutes, until pastry is puffed and golden and sausages are cooked.