Chocolate and hazelnut paris-brest

For the crème mousseline, warm the milk in a large pan over a medium-high heat until steaming. Meanwhile, put the yolks, vanilla, sugar and cornflour into a bowl and whisk together for a couple minutes or until it forms a smooth, pale paste. Gradually pour in the milk, whisking as you do to prevent curdling. Scrape the custard back into the pan and cook over a medium heat, whisking constantly, until the custard is thickened and bubbling. Cook for 2 minutes more to ensure the cornflour is cooked out, then scrape into a bowl. Add 50g of the butter and quickly stir together to combine. Cover with a piece of baking paper touching the surface and refrigerate for a few hours until thoroughly chilled.

Once the custard is chilled, put the remaining butter into a large bowl and, using an electric mixer, beat until smooth and creamy. With the mixer running, add the thickened custard in four additions, beating until smooth before adding more. Finish by adding the Nutella and beating until fully combined and lump-free. Scrape into a container and refrigerate until needed.

To make the choux pastry, put the milk, sugar, butter, ¼ tsp of fine sea salt and 55ml of water in a medium pan over medium heat and bring to a full rolling boil, by which point the butter should be fully melted. Remove the pan from the heat, add the flour and stir together quickly with a wooden spoon to form a dough. Put the pan back on the heat and stir the dough for 2-3 minutes to dry it out slightly. Tip the dough into a large bowl and beat for a few minutes to cool it down, so that when the eggs are added they don’t scramble.

Add the eggs a little at a time, beating well between each addition. Add enough so that the pastry is shiny but still holds its shape. Scrape into a piping bag fitted with a large plain round piping tip.

Heat the oven to 180C/fan 160C/gas 4. Line a large baking tray with baking paper or a silicone baking mat and draw a 20cm circle in the middle, then turn the baking paper over. Pipe a ring of choux pastry so it sits along the circle then a second inside the first circle making sure the two are touching. Pipe a third ring atop the first two so it sits in between the two. Brush the pastry with a beaten egg and then sprinkle liberally with hazelnuts. Bake in the oven for 35 minutes or until a rich golden brown. Turn off the oven but prop the door open with a wooden spoon, leaving the choux pastry inside to cool slowly.

Remove the choux pastry from the oven and, once fully cooled, use a serrated knife to cut through the middle of the pastry, cutting it into two rings. Put the crème mousseline into a piping bag fitted with a star tip and pipe the filling into the bottom half of the choux pastry, sandwiching together with the top piece. Dust with icing sugar and serve. Once assembled, the paris-brest is best kept refrigerated until ready to serve, but is best on the day.