Liquamen is the ancient Roman equivalent of fish sauce. If you cannot find authentic liquamen, a high-quality Asian fish sauce or a mixture of white wine and salt (as noted in the ingredients) works as a historical approximation.
Defritum is a thick paste made from breadcrumbs, herbs, oil, and sometimes nuts or cheese. It acts as a flavorful glaze or sauce base. You can make a simple version by mixing toasted breadcrumbs with olive oil and herbs.
Saturei refers to savory, likely winter savory, which has a peppery, thyme-like flavor. If unavailable, a mix of thyme and sage is a suitable substitute.
This recipe is based on Apicius’ "De Re Coquinaria," specifically Book 1, Recipe 10.