Make the dough
Cut the cold butter into cubes. In a food processor, combine the spelt flour, brown sugar, butter, and a pinch of salt. Mix until you get a crumbly mixture. Then add ice-cold water in small amounts until the dough comes together.
Chill the dough
Briefly knead the dough into a ball, flatten it into a square, wrap in cling film, and refrigerate for at least 1 hour.
Prepare the filling
Finely chop the onion and crush the garlic. In a bowl, mix the lamb mince with the onion, garlic, chopped parsley, and crumbled feta. Season with freshly ground pepper and Maldon sea salt.
Roll out the dough
Dust your work surface with flour. Roll out the chilled dough into a rectangular sheet about 3 mm thick.
Form the sausages
Cut 5 × 5 cm squares from the dough. Roll small sausages of about 5 cm long from the lamb mixture and place them diagonally on the dough squares.
Seal the dough
Brush the corners of the dough with a little water, fold over, and press the top firmly so everything is well sealed. Place the filled dough pieces next to each other on a baking tray.
Apply the glaze
Beat the egg yolk with a splash of milk and a pinch of salt. Brush each roll with this mixture so they turn beautifully golden during baking.
Bake
Preheat the oven to 190 °C and bake the sausage rolls for about 25 minutes until golden brown.
Serve
Let the sausage rolls rest briefly so the filling sets slightly, then serve warm as a snack or appetizer.