Preheat your oven to 200C/180C fan/gas 6. Crush the garlic clove with a pinch of salt into a paste using a pestle and mortar, or alternatively, flatten it with the side of a knife on a cutting board. Combine the garlic paste with the chopped parsley and stir in 50ml of cold water.
If using sausages, peel off the skins. Process the sausagemeat in a food processor on high speed, adding the garlic-parsley water to the mix. Season with pepper and blend until well combined.
Lay the puff pastry on a board and slice it lengthwise into two equal strips.
Divide the sausagemeat mixture into two portions and shape each into a long cylinder. Place one cylinder along the length of each pastry strip, leaving a 1cm border.
Roll the pastry tightly around the sausagemeat, using the beaten egg to seal the edges.
With a sharp knife, cut each roll into 10 pieces, each approximately 2.5cm in length. Arrange the pieces on a baking sheet. These can be covered and frozen for up to one month.
Brush the tops of the rolls with the remaining beaten egg. Bake in the oven for 25-35 minutes until the pastry is puffed and golden, and the sausage filling is thoroughly cooked. If baking from frozen, allow an additional 10 minutes. Serve hot or cold, accompanied by tomato ketchup if desired.