First, whip the cream until it is firm and put in the fridge to chill.
Next, set up 3 bains marie (3 bowls over gently boiling water). Put one kind of chocolate in each bowl. The water should not touch the bottom of the bowl.
Add 50g of butter into each bowl and let the butter and chocolate gently melt together, do not stir. Once melted, take off the heat, stir with a fork to combine the butter and chocolate, then leave to cool.
Once the butter and chocolate are cool enough, about body temperature, stir an egg yolk into each bowl. If the chocolate is too hot the eggs will scramble so take care.
Take out the whipped cream and divide into 3. Into one portion, if you wish you can stir in some Drambuie, and fold it into the white chocolate mixture. Fold the other two portions of whipped cream into the milk, and dark chocolate.
Now you have three kinds of mousse. Spoon the milk chocolate mousse into glasses, followed by a layer of white chocolate mousse, and top with the dark chocolate mousse. Top with some grated dark chocolate if you wish.
Allow the mousse to chill for a couple of hours before serving. And have the doctor's phone number handy.