In a bowl, mix flour, butter, and water to form a soft dough. Let it rest for 20 minutes.
Divide the dough into small portions and flatten each piece.
Place a spoonful of winter melon paste mixed with sugar in the center.
Fold and seal the dough to form a round pastry.
Gently flatten the pastry and place it on a baking tray.
Brush the top with egg wash and sprinkle sesame seeds.
Bake in a preheated oven at 180°C (350°F) for about 20–25 minutes until golden brown.