Liebstockel (Birthwort) is difficult to find in modern grocery stores. If unavailable, you can substitute with a mix of dried chervil and parsley, or simply increase the coriander and add a pinch of dried rosemary for herbal depth.
Liquamen is a fermented fish sauce used in ancient Rome. Modern fish sauce (like Vietnamese Nuoc Mam) or a high-quality anchovy paste dissolved in water are excellent substitutes. If using salt, add it to taste, as the liquid will be less savory.
Leftovers can be stored in an airtight container in the refrigerator for up to 3 days. The flavors often deepen and meld beautifully overnight, making this a great make-ahead dish.
For a richer sauce, you can reduce the cooking liquid by half before thickening with starch.