Warm 100 ml of milk in a pot lukewarm. Sieve 500 g flour into a large mixing bowl. Add vanilla sugar and 1 pinch of salt. Crumble the yeast and mix with sugar until the yeast dissolves and becomes liquid.
Add yeast, lukewarm milk and 3 eggs to the flour in the bowl and knead with the dough hooks of the mixer for about 5 minutes. Add 150 g butter in small pieces and knead until you have a smooth dough.
Cover well with cling film so that the dough does not dry out. Leave to rise in a warm place for about 50 minutes. The dough volume should double during this time.
Grease a box mould (25 cm long; 1.9 l capacity) and dust with flour. Knead the dough again with lightly floured hands on a floured work surface. Form a roll (approx. 40 cm long) and cut into 8 pieces.
Form pieces on the work surface into 8 balls with loose circular movements. Place them side by side in the box mould. Cover and leave to rise again in a warm place for about 30 minutes.
Preheat oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer). Whisk egg yolk and 1 tbsp. milk. Carefully brush the dough with it. Bake in the hot oven for about 40 minutes. Cover with aluminium foil after about 30 minutes.
Remove the brioche. If it sounds hollow when you knock on it, she's done. Leave to cool briefly on a cake rack. Then carefully loosen the edge and fall out of the mould. Let it cool down.
Pretty for guests are small brioche rolls with "head"
Roll the dough into 14 balls. Press 1⁄4 with the edge of your hand, rolling back and forth to form a small "head".
Grab his head, pull up. Press a depression into the lower dough ball and place the head inside. Press the lower dough piece flatter around the head. Place in a brioche mould (approx. 9 cm Ø) and let it rise. Spread with egg milk and bake for about 15 minutes.
With taste: The dough can be refined with orange blossom water, grated zest of 1 organic lemon or almond liqueur. Who likes, knead in 125 g chocolate chips or raisins.
Egg spread in French: Instead of milk, whisk egg yolk with cream or double cream.
Sleepy people can prepare the dough the evening before and let it rise in the refrigerator overnight, covered. Form and bake the next morning - you will have oven-warm brioche for breakfast.
Poor knights, sweet or savoury casseroles can be prepared from brioche leftovers.