01 - Fill a medium saucepan with approximately 2 inches of water and bring to a gentle simmer over medium heat. This creates your double boiler base for gentle, indirect cooking.
02 - In a large heatproof bowl, combine the egg yolks and granulated sugar. Whisk vigorously for approximately 2 minutes until the mixture becomes pale yellow and slightly thickened in consistency.
03 - Place the heatproof bowl over the simmering water, ensuring the bottom of the bowl does not come into direct contact with the water surface. This gentle heat prevents curdling while cooking the custard.
04 - While whisking continuously, gradually pour in the Marsala wine (or dry sherry). Maintain steady whisking to incorporate the wine evenly and create a smooth emulsion.
05 - Continue whisking persistently for 8 to 10 minutes over the gentle heat. The mixture will triple in volume and form thick, soft ribbons when the whisk is lifted. The custard should register approximately 160°F on an instant-read thermometer for proper pasteurization.
06 - Remove the bowl from the heat promptly. Divide the warm zabaglione among dessert glasses or serving bowls and serve immediately while still warm and frothy.
07 - If desired, garnish with fresh berries or serve alongside ladyfingers or biscotti for dipping. The classic preparation emphasizes the pure custard, but accompaniments provide texture contrast.