Ingredients
200g dark chocolate
75g salted butter
50g crème fraîche
50g icing sugar, plus 2 tbsp icing sugar
4 medium eggs
A pinch of salt
100ml double cream

A jar or tin of sweetened chestnut cream (optional)

For the sponge fingers:
4 medium eggs
120g caster sugar
100g plain flour, sieved
Icing sugar, for dusting

(Alternatively, use ready-made sponge fingers)

Method: For the sponge fingers:

1. Preheat the oven to 180°C/fan 160°C/gas 4.
      
2. Separate the egg yolks from the whites and set aside the yolks. Add just the whites to the bowl of your electric mixer. Whisk with a pinch of salt until the mixture forms soft peaks, then start to gently add the sugar. Whisk to a thick, meringue-like consistency.
      
3. Add the egg yolks and mix for a further 30 seconds.
      
4. Add the sieved flour all in one go and use a spatula to gently mix, trying not to deflate the mixture too much.
      
5. Pour the mixture into a piping bag with a star-shaped or round nozzle. On a tray lined with baking paper, pipe the long, sponge finger shapes. You will need multiple trays for this.
      
6. Sprinkle generously with icing sugar, then bake for 15 minutes until lightly golden.
      
7. Leave to cool down on the tray, then set aside to fully cool.

Method: For the Charlotte

1. First make the chocolate mousse. In a bowl, add the chocolate, butter, crème fraîche and 50g icing sugar. Melt together in a microwave, or in a small heat-proof bowl resting over a pan of simmering water.
      
2. Divide the eggs and set aside the yolks.
      
3. Whisk the egg whites with a pinch of salt until stiff peaks form. Add the egg yolks to the chocolate mix and stir until combined.
      
4. Combine the egg whites with the chocolate mix, stirring as gently as possible to keep the mixture airy and light.
      
5. Grease a 10cm–12cm springform cake tin (tall enough to accommodate most of the height of the sponge fingers), and line with baking paper.
      
6. Working one at a time, arrange the sponge fingers in a ring around the edge of the tin. Use more to cover the base, cutting to size as needed.
      
7. Add 2 tbsp of chestnut cream (if using) on top of the sponge base and top with half of the chocolate mousse. Add another layer of fingers and cover with another 2 tbsp of chestnut cream and finish with the remaining mousse. Chill in the fridge for at least 4 hours.
      
8. Once set, carefully unclip and remove the tin. You can leave on the base for ease.
      
9. Make a Chantilly cream by whisking the cold double cream with an electric mixer or whisk, slowly adding 2 tbsp of sugar a little at a time. After 2–3 minutes, the Chantilly should be thick enough to pipe.
      
10. Pipe the mixture on top of the mousse or use a spatula to dollop on top. Serve extra cold. Bon appétit!