If Passum (Roman grape must) is unavailable, substitute with a high-quality sweetened red wine reduction or a mixture of honey and red wine vinegar.
Liquamen was a fermented fish sauce. For a modern substitute, use fish sauce, soy sauce, or simply salt as indicated.
This dish can be served warm or at room temperature. Store leftovers covered in the refrigerator for up to 2 days.
For a richer texture, you can add a splash of cream or milk to the egg mixture.