01 - Fill a medium saucepan with approximately 2 inches of water and bring to a gentle simmer over medium heat.
02 - In a large heatproof bowl, whisk together the egg yolks and granulated sugar until the mixture becomes pale yellow and slightly thickened, about 2 minutes.
03 - Place the bowl over the simmering water, ensuring the bottom of the bowl does not touch the water surface.
04 - Gradually pour in the Marsala wine while whisking continuously to prevent curdling.
05 - Maintain steady whisking for 8 to 10 minutes until the mixture triples in volume and forms thick, soft ribbons that hold their shape when the whisk is lifted.
06 - Remove the bowl from heat and portion the warm zabaglione into dessert glasses or small bowls.
07 - Top with fresh berries or serve alongside ladyfingers or biscotti for dipping, if desired.