Preheat the oven to 200C/180C Fan/Gas 6. Line three baking sheets with baking parchment.

In a heavy saucepan, melt the cubed butter in 250 ml water over medium heat. Bring to a boil. Remove from heat; add sifted flour and stir until a soft ball forms. Return to low heat and cook for 3–5 minutes, stirring constantly. Let cool slightly.

Transfer mixture to a mixer bowl with whisk attachment. Gradually whisk in the eggs, one at a time, until smooth. Fill a piping bag fitted with a 1½ cm plain nozzle with the mixture.

Pipe twelve small mounds onto each baking sheet (total 36). Smooth tops with a wet finger. Bake for 10 minutes, then reduce oven to 190C/170C Fan/Gas 5 and bake for another 10 minutes until golden brown. Pierce each bun to release steam, return to oven for 5 minutes to dry out. Cool on a wire rack.

Heat milk in a pan to boiling, then let cool for 30 seconds. Whisk egg yolks with caster sugar until pale. Add cornflour, cinnamon, and nutmeg; whisk to combine. Gradually pour warm milk into egg mixture, whisking continuously. Return to pan and cook over medium heat, whisking until thick and boiling. Remove from heat, transfer to bowl, cover with cling film and cool.

Heat double cream until simmering, pour over broken chocolate, and stir until smooth. Cool until thick enough to drizzle.

Pipe melted white chocolate into snowflake shapes on parchment and let set.

Whip double cream to soft peaks, then fold into cooled crème pâtissière. Fill a piping bag and pipe into cooled choux buns.

Boil caster sugar with 5 tablespoons water until golden (170C on a thermometer). Remove from heat and cool slightly.

Arrange 14 choux buns in a circle, then place 10 buns inside to form a smaller circle. Dip one side of each bun in caramel, sticking them together to form a wreath.

Dip bases of remaining 12 buns in caramel and place on top of the wreath.

Line a baking sheet with silicone paper. Reheat caramel, add red food colouring, then stir in hazelnuts. Place individual hazelnuts on the silicone paper to cool.

Drizzle one quarter of the chocolate ganache over the wreath. Transfer to serving plate and decorate with white chocolate snowflakes and caramel-coated hazelnuts. Serve immediately.