Cracknel

Mix all the ingredients together to form a smooth dough. Roll it out on greaseproof paper to a thickness of about 3mm. Use a pastry cutter to cut out 3cm discs, and place these in the freezer.

Choux buns

Sieve the flour and add the salt and sugar.
Put the milk, water and butter in a pan and bring to the boil. Add the flour gradually and continue cooking for about 3 minutes, stirring all the time with a wooden spoon to keep the mixture smooth. A slight crust will form on the bottom of the pan.
Transfer to a planetary mixer and use the paddle attachment to continue mixing at a moderate speed until the dough is cold.
Carefully pour in the first egg, stirring all the time. Make sure it's well incorporated in the dough before adding the second one. Try to make sure the dough is smooth and even.
Transfer to a pastry bag with a smooth nozzle (1cm diameter). Form small balls of about 8g (2.8cm diameter).
Place a frozen cracknel disc on top of each bun.
Bake straight away at 185°C for about 15 minutes.

Filling

When they're cold, fill each choux bun with 7.5g of Nutella.