1Crème pâtissière: heat 500 ml milk with vanilla. Whisk yolks, 100 g sugar and cornflour, pour in the hot milk, return to the pan and whisk until thick and bubbling for a minute. Stir in 20 g butter, cover with film and chill.
2Choux: bring water, 125 ml milk, 100 g butter, salt and 5 g sugar to a boil. Tip in the flour and beat over low heat.
3Cool 5 minutes, then beat in the eggs one at a time.
4Pipe 12 cm lengths on a lined tray. Bake at 200 C for 15 minutes, then 180 C until deep golden. Do not open the oven early.
5Cool, poke holes underneath and pipe in the crème pâtissière.
6Melt chocolate with warm cream and dip the tops. Chill to set.
Serve it like this
Line up on a long plate or board, chocolate side up, chilled. Serve with coffee.