Preparation of the dough: Mix the yeast with the lukewarm water. Let the vitamin C dissolve well in the cold water. Put the flour, salt and sugar in a large bowl and rub the fat into it. Then mix the yeast liquid and the cold water with the dry ingredients and form a smooth, pliable dough. Knead the dough ball on a floured surface for 10 min (2-3 min with a food processor) until it is nice and smooth. Form a ball of dough and leave in a warm place, with the lid closed, for 5 min.
Preparation of the manchets: divide the dough into 12 pieces. Knead and shape each piece into an elongated bread roll. Place on a baking sheet lined with parchment paper and score diagonally a few times with a sharp kitchen knife. Sprinkle with milk, cover and let rise. Bake on the top rack in a heated oven at 230 °C (gas mark 4) for 15-20 minutes. Cool on a roasting rack.