Preheat oven to 200°C (400°F) and line a large baking tray with parchment paper.

In a medium bowl, combine the sausage meat with dried sage and black pepper until evenly incorporated.

Unroll the puff pastry onto a lightly floured surface and cut it in half lengthwise into two long rectangles.

Divide the sausage mixture into two equal portions and shape each into a long cylinder positioned along the center of each pastry strip.

Whisk the egg and water together in a small bowl to create an egg wash.

Brush the long edge of one pastry strip with egg wash, then fold the pastry over the meat to seal, pressing down firmly to secure the seam. Repeat for the second strip.

Cut each long roll into four equal sections to create eight individual rolls total.

Place the rolls onto the prepared baking tray, brush the tops with the remaining egg wash, and sprinkle with poppy seeds.

Bake for 20 to 25 minutes until the pastry is puffed and deep golden brown, and the internal temperature of the sausage reaches 71°C (160°F).

Remove from the oven and allow to cool on a wire rack for 5 minutes before serving.