Preheat Oven: Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper.
Prepare the Filling: In a large bowl, combine ground pork, grated apple, chopped onion, minced garlic, thyme, nutmeg, salt, and pepper. Mix well until all ingredients are evenly incorporated.
Prepare the Puff Pastry: Roll out the puff pastry on a lightly floured surface into a rectangle (~12x10 inches). Cut the pastry into two long strips, lengthwise.
Assemble the Sausage Rolls: Divide the filling evenly between the two strips, placing it in a line along one edge of each strip. Fold the pastry over the filling and press edges to seal. Use a fork to crimp the edges. Cut each roll into 6–8 smaller pieces for bite-sized rolls or leave as long rolls for larger servings.
Apply Egg Wash: Brush the tops of the sausage rolls with beaten egg. Sprinkle with sesame seeds or poppy seeds if desired.
Bake the Sausage Rolls: Place on prepared baking sheet and bake for 25–30 minutes, or until pastry is golden brown and cooked through.
Cool and Serve: Let cool slightly before serving warm.