Lay the sponge fingers in the dish and pour over coffee and liqueur. Chill.

Whisk egg and yolks and pass through a sieve. Whisk sieved egg into a roomy bowl with vanilla and sugar until foaming.

Mix cornflour to a smooth paste with 3-4 tablespoons of cold milk taken from the measured amount.

Warm milk and cream in a small heavy bottomed pan until almost boiling.

Pour into the cornflour paste, whisking gently throughout.

Now whisk milk, cream and cornflour mixture gently into the combined eggs, sugar and vanilla.

Wash out pan and return mixture to the heat. Cook gently, stirring gently constantly with a wooden spoon changing to a whisk as the mixture starts to thicken.

Once thickening, turn off heat and whisk until smooth and creamy. Cool slightly and pour over sponge fingers. Chill for several hours until set.

Whisk cream into soft peaks and spread over custard. Chill again and dust with drinking chocolate before serving.

For complete perfection, serve with strawberries and a small coffee on the side.