First, make the dough.
Cut the cold butter into cubes.
Put the flour, cane sugar, and butter with a pinch of salt in a food processor and pulse until crumbly. Do not process for too long, as the dough will become warm and tough.
Add the water gradually until you form a ball.
Knead the dough briefly into a flat square, wrap it in plastic wrap, and place it in the refrigerator for at least 1 hour to firm up.
Preheat the oven to 190 °C.
Peel the onion and garlic and finely chop them.
Mix the minced meat with the onion, garlic, and parsley.
Crumble the feta and add it. Mix. Season with pepper and salt.
Dust the work surface and the dough with flour and roll out the dough into a more or less rectangular sheet about 3 mm thick.
Cut squares from the dough measuring 5 cm by 5 cm.
Roll small sausages of 5 cm from the minced meat and place them diagonally on the squares of dough. Put some water on the corners of the dough and fold them closed. Press well at the top. Place the filled dough squares close together on a baking sheet.
Beat the egg yolk with a splash of milk and some salt.
Brush the dough with the egg yolk so that the sausage rolls color nicely and stay together well.
Bake the sausage rolls in the oven for 25 minutes.