Place the milk and dark chocolate in separate heat proof bowls, melting each over a pot of barely simmering water.

Add 2 tablespoons of cream to another heat proof bowl. Add the white chocolate and stir gently to mix while melting over another pot of simmering water.

In a large bowl, beat 250ml cream just until soft peaks form. Divide cream into three separate medium sized bowls and fold each type of cooled chocolate into each one.

Whip egg whites in a large clean bowl until soft peaks form.

Divide whipped egg whites into three and fold into the three separate chocolate and cream mixtures, being careful to gently fold to avoid beating out the air.

Spoon dark chocolate mousse into 6 or 8 glass cups (depending on their size), then top with a layer of the milk chocolate mousse, and finally, the white chocolate mousse.

Place in the fridge to chill, between 15-30 minutes. Alternatively, you can fill three plastic piping bags with each mousse and simply pipe the mousse into each glass.

Heat the remaining 100g Butlers Dark Chocolate Bar in the microwave on lowest power setting for 10 second bursts, just until chocolate has softened slightly, but isn't melting. Use a vegetable peeler or sharp knife to shave chocolate curls.

Top off each mousse with chocolate shavings before serving. If mousse has been chilled for longer 30 minutes, leave to stand at room temperature for between 10-20 minutes before serving. Mousse can be prepared up to 2 days ahead and kept chilled in the fridge covered with Clingfilm. Leave mousse to stand at room temperature for 30-40 minutes before serving.