Preheat the oven to the temperature on the puff pastry packet (usually 200 °C).
If using a meat filling, heat 1 tbsp of lard, soften the onion in it, add the minced meat, season with salt and pepper and fry until browned; skip this step for the ham filling.
Mix the ham (or the fried meat) with the sour cream and season with salt and pepper.
Roll out the puff pastry on a lightly floured surface and cut it into rectangles (about 10x15 cm).
Spread a finger-thick strip of filling along the long side of each piece.
Fold the pastry over to form a small, long roll and press the edges together.
Put the rolls on a tray lined with baking paper and brush the tops with beaten egg.
Bake for 20-25 minutes until nicely golden.
Serve warm as a starter or a light supper.
Based on: A jó házikonyha (a classic Hungarian cookbook), modernised. Calories and protein are estimated.