1. In a large bowl, whisk together the egg yolks and sugar until the mixture has become paler and much thicker. 2. Gradually add your alcohol of choice to the egg mixture, little bits at a time, whisking after each. 3. Place the bowl of a pan of gently simmering water and continue to whisk for another 6 or 7 minutes, until the mixture is thick (don't be tempted to under-beat it, otherwise the zabaglione will separate). The mixture should leave a thick trail on the surface when you lift the whisk. 4. Pour the mixture into four warm bowls/glasses and serve straight away, with or without the amaretti.