Prepare your work area. Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper. Remove puff pastry from the refrigerator about 10 minutes before using to slightly soften.
Make the festive sausage filling. In a large bowl, combine the sausage meat, finely diced onion, chopped cranberries, sage, thyme, nutmeg, cloves, breadcrumbs, and seasoning. Mix thoroughly with your hands until all ingredients are evenly distributed.
Roll out the pastry. Unroll your puff pastry sheets on a lightly floured surface. If using block pastry, roll it into rectangles approximately 12 x 14 inches.
Form sausage logs. Divide your sausage mixture into four equal portions. Form each portion into a long cylindrical shape and place along the long edge of each pastry sheet, leaving a 1-inch border.
Prepare the egg wash. Beat the egg with 1 tablespoon of milk in a small bowl.
Seal the rolls. Brush the pastry edge with egg wash, then fold the pastry over the sausage mixture and seal by pressing with a fork. The seal should be on the bottom.
Cut into portions. Use a sharp knife to cut each long roll into 6 equal pieces, making 24 individual sausage rolls.
Apply final touches. Transfer the rolls to your prepared baking sheet. Brush the tops with remaining egg wash and sprinkle with sesame or poppy seeds if using. Make a small slit in the top of each roll for steam to escape.
Bake to golden perfection. Bake in the preheated oven for 20-25 minutes until the pastry is puffed and golden brown and the meat is thoroughly cooked.
Rest before serving. Allow to cool for 5 minutes before serving, as the filling will be extremely hot.