Soak the stale roll in water for 5 minutes, then squeeze out excess water. Meanwhile, finely chop the parsley and onion. Heat the butter in a pan over medium heat and fry the chopped onion for 3 minutes until softened.
In a large bowl, combine the squeezed roll, fried onion, chopped parsley, minced meat, 1 egg, salt, pepper, and paprika powder. Mix well. Add the roughly chopped sauerkraut, ham cubes, and grated cheese, and mix until evenly combined.
Thaw the frozen puff pastry at room temperature for 15-20 minutes (or according to package instructions). Roll it out on a clean work surface into a thin sheet approximately 35 cm x 30 cm. Spread the meat mixture evenly over the pastry, leaving about 1 cm of space around the edges.
Roll up the pastry tightly along the longest side to form a log. Whisk the second egg and brush it evenly over the surface of the pastry roll.
Bake at 180°C (350°F) for 50-60 minutes until the pastry is golden brown and the filling is cooked through.