Croquembouche (Caramel Choux Tower)

Pastry cream. beat the yolks, sugar, cornflour and salt together in a large pan until smooth, then pour in the milk slowly, whisking. Cook over medium heat, whisking all the time, until it is very thick and bubbles for 1 min; it will pass 85 °C. Sieve, whisk in the butter and vanilla, press cling film onto the surface and chill at least 3 h.

Choux. heat the oven to 200 °C (180 °C fan) and line the trays. Bring the butter, water, milk, sugar and salt to a full boil in the large pan, take off the heat and beat in all the flour. Return to low heat and stir for 2 min until the paste forms a ball. Cool 5 min, then beat in the 6 eggs a little at a time until glossy and the paste falls from the spoon in a thick V; add some of the extra egg only if it is still stiff.

Crackle topping. an hour or more ahead, beat the butter, brown sugar and flour into a smooth dough. Roll it between 2 sheets of baking paper to 2 mm thick and freeze flat until hard, at least 30 min. The thin sugar crust cracks as the puffs rise and keeps them round and even.

Pipe. pipe about 60 balls 3 cm across, 4 cm apart, and smooth any peaks with a wet finger. Cut 3 cm discs from the frozen crackle sheet with the cutter and lay one on top of each ball.

Bake. bake one or two trays at a time for 25-30 min, without opening the door for the first 20 min, until deep golden and dry. Poke a hole in the base of each with the skewer and put them back in the switched-off oven, door ajar, for 10 min to dry. Cool on the rack.

Fill. whip the cold cream to soft peaks. Beat the pastry cream smooth and fold in the whipped cream. Fill each puff through its hole with the 6 mm nozzle until it feels heavy, and chill the filled puffs while you make the caramel.

Cone. roll the card into a 35 cm tall cone with a 20 cm wide base, tape it, cover it with baking paper and brush the paper lightly with oil. Stand it on the cake board.

Caramel. stir the sugar, water and lemon juice in the heavy pan, then boil without stirring, swirling now and then, until it is a deep amber, about 170 °C. Dip the base of the pan in the cold water for 3 s to stop it cooking. Hot caramel causes serious burns, so wear gloves, work slowly and keep children away.

Build. dip one side of each puff in caramel and stick it to the board round the base of the cone, the rounded tops facing out, to make a ring. Build up ring after ring, each slightly smaller, setting the puffs in the gaps of the row below, until you reach the top; finish with one puff. Warm the caramel gently if it gets thick. Building on a cone keeps the tower straight and stable.

Finish. let the last of the caramel cool for a few minutes until it falls from a fork in a thread. Dip the fork and wave it quickly back and forth round the tower so fine golden strands wrap it. Serve within 2 h of building, breaking off the puffs. Keep any leftover filled puffs in the fridge and eat within 1 day.