Preheat the oven to 200C/fan 180C/gas 6.

Butter a 22 x 31cm Swiss roll tin and line it with buttered baking paper.

Dust the tin with cocoa.

Using electric beaters, beat eggs and sugar for 7 minutes until thick enough to hold a trail.

Fold in flour and sifted cocoa.

Swirl in melted butter and fold through.

Pour into the prepared tin and bake for 10 minutes until just firm.

Cool under a clean tea towel.

Beat egg yolks with sugar until thick and pale.

Melt the dark chocolate and loosely whip the cream until it holds its shape.

Beat half the cream and all of the chocolate into the egg mixture, then gently fold in the remaining cream.

Whisk the egg whites until softly peaked, then fold them into the chocolate mixture.

Grease a 1.4 litre/2½ pint basin with a little oil.

Line it with cling film, letting it overhang.

Cut a circle of sponge to fit the bottom of the basin and place it inside.

Cut seven sloping rectangles about 10cm long from the sponge and fit them tightly together around the bowl.

Sprinkle with most of the coffee and Tia Maria mix.

Fill the bowl halfway with the mousse, then top with a snug-fitting circle of cake.

Sprinkle with the remaining coffee mix.

Spoon in the rest of the mousse, then cover with the overhanging cling film.

Chill for at least 4 hours until firm (ideally overnight).

Heat all topping ingredients gently in a bowl over a pan of simmering water until the chocolate melts.

Leave to cool, stirring occasionally, until thick and glossy.

Spread the topping all over the turned-out pudding.

Top with chocolate-covered cocoa beans and chocolate curls.

Leave the pudding out of the fridge for about 20 minutes before serving to let the mousse relax to a chocolatey velvet.