Preheat the oven to 175°C (350°F) using the fan setting. Butter the base of a 23 cm (9-inch) cake tin and line it with baking parchment.

In a medium-sized bowl, dissolve the cocoa powder in the boiling water. Add the instant coffee and vanilla extract, and stir well. Set aside to cool.

In a small saucepan, melt the butter over low heat. Set aside to cool slightly.

Using a stand mixer, beat the eggs and sugar on high speed for about 10 minutes, until the mixture becomes very light, fluffy and triples in volume.

Add approximately one cup of the beaten egg mixture to the bowl containing the cocoa mixture. Add the melted butter and stir until combined.

Sift the flour directly into the bowl with the remaining egg mixture. Using a large spoon or spatula, gently fold the mixture with circular movements from the bottom upwards until the flour is incorporated. Be careful not to lose too much volume from the eggs.

Add the cocoa mixture and fold it in gently using the same technique.

Pour the batter into the prepared cake tin and bake in the preheated oven for 30–35 minutes. To check whether the cake is done, insert a wooden skewer into the centre. If it comes out clean and dry, the cake is ready.

Run a spatula around the edges of the tin to loosen the cake. Leave it to cool in the tin for 10 minutes. Then turn it out onto a wire rack and remove the baking parchment from the base.

Carefully turn the cake over again onto two pieces of cardboard or flat plates, and leave it to cool completely.

Mix the cornflour with a little of the milk until smooth.

Pour the remaining milk, heavy cream and sugar into a saucepan. As soon as the mixture begins to boil, add the cocoa powder and whisk until fully dissolved.

Once the mixture starts bubbling, remove the saucepan from the heat and add the dark chocolate. Leave it to stand for a few minutes, then stir until the chocolate has melted and is fully incorporated.

In the bowl of a stand mixer, beat the eggs with the dissolved cornflour mixture. Slowly pour in the hot milk mixture, whisking continuously.

Return the entire mixture to the saucepan and cook over medium-low heat, stirring constantly, until the cream comes to a gentle boil and thickens.

Remove from the heat and add the butter. Stir until it has melted and the cream is smooth and homogeneous.

Transfer the cream to a bowl and cover its surface with cling film, making sure the film touches the cream directly. This prevents a skin from forming.

Once the cream has cooled to room temperature, refrigerate it for 12–24 hours.

Whip the heavy cream for the topping together with the icing sugar until thick and fluffy. Set aside.

Choose a glass trifle bowl and cut the chocolate sponge cake into small cubes.

Arrange half of the sponge cubes over the bottom of the bowl. Drizzle with 2 tablespoons of the hazelnut liqueur, then scatter half of the chopped Ferrero Rocher chocolates over the sponge.

Cover with half of the chocolate pastry cream, followed by half of the whipped cream.

Repeat the layers with the remaining ingredients, finishing with the whipped cream on top.

Refrigerate the trifle for 12–24 hours before serving, allowing the flavours to develop and the layers to set beautifully.

Enjoy this decadent, luxurious dessert!