Begin by making the craquelin. In a bowl, rub together the flour, sugar and cold butter using your fingers until it forms a fine crumb. Keep working until all the ingredients come together to form a uniform dough. Roll out the dough between 2 sheets of baking paper to 2-3mm thick. Chill in the fridge for at least 30 minutes (see Make Ahead).

Next, make the choux pastry. Heat the oven to 190°C/170°C fan/gas 5. Add the butter, milk, sugar, salt and 100ml water to a medium saucepan over a medium heat. Bring to a rolling boil for 30 seconds, then take the pan off the heat and, using a wooden spoon, quickly stir in the flour for about a minute until fully combined. The mixture needs to come away from the edge of the pan into a smooth dough.

Transfer the dough to a bowl to cool down slightly, then slowly incorporate half the beaten eggs. Once combined, add the remaining eggs and continue to beat until the mixture is smooth and pipeable. To check, pick up some dough with the spoon and tilt it sideways – the dough should be trying to fall off the spoon but not quite doing it. Transfer 200g of the choux dough to a piping bag fitted with a 1cm nozzle – the rest can be kept for another recipe.

Line a baking tray with baking paper or a baking mat and mark out a 14cm diameter ring (either by drawing it with a pencil or using a plate or baking ring and dusting icing sugar around it. Using this mark as a guide, pipe 8 or 9 regular 3cm diameter domes to form a necklace/circle of choux domes, spacing them 5mm apart. This will leave space for the choux to expand, and the buns will stick to each other as they bake.

Take the craquelin out of the fridge and use a 3cm round cutter to cut out 8 or 9 discs. Lightly press one on top of each choux pastry dome. Bake for 35-40 minutes until golden brown, then set aside to cool.

Meanwhile, begin making the praline paste. Put a medium saucepan over a medium heat. Once hot, gradually add the sugar and heat, swirling rather than stirring, until it melts and forms a light brown caramel. Put the hazelnuts on a tray lined with baking paper, pour the caramel over the top, then leave to cool and set.

To make the filling, start by making a pastry cream (crème pâtissière). Add the milk, vanilla seeds and pod to a saucepan with 1 tsp of the sugar and bring to the boil. Whisk together the remaining sugar, egg yolks and cornflour in a heatproof bowl.

As soon as the milk boils, remove it from the heat and whisk a quarter of it into the egg yolk mixture. Return this mixture to the pan of milk, whisking continuously. Put back over a medium heat andcontinue whisking until the mixture starts to thicken, then remove from the heat again and continue to whisk until smooth.

Return the pan to the heat and bring the mixture back to the boil. Cook for 1 minute, then remove from the heat and remove the vanilla pod. Using a rubber spatula, transfer the pastry cream to a tray lined with baking paper (this will help it to cool quicker). Cover the pastry cream, then allow to cool and chill until needed. You’ll need 180g for this recipe – any left over can be used in another recipe (See ‘Don’t waste it’).

Once the praline has cooled and set, break up the nuts and caramel and set aside 70g to use later. Put the remainder in a food processor along with the hazelnut oil and 2 small pinches of salt, then whizz to a paste.

Put the 180g pastry cream in the bowl of a stand mixer with a whisk attachment and whisk until smooth. Add 170g of the praline paste and the kirsch, whisk again to combine, then gradually add the butter, whisking constantly, until smooth, aerated and pipeable. Transfer to a piping bag with a 1.5cm nozzle. Transfer the rest of the praline paste to a second piping bag with a 1.5cm nozzle.

Slice the cooled choux necklace horizontally two thirds of the way up and set the top aside. Pipe the praline paste into the base of the choux buns, then top each one with a generous dome of the pralined pastry cream filling. Sprinkle over some of the reserved caramelised hazelnuts and put the top of the choux necklace back on top. Put the Paris-Brest in the fridge for 30 minutes or so to set. Just before serving, dust with icing sugar