A short entry today, it’s been a long day
p. 556 of fish
(…) The diversity of fish according to the manner of their cooking is multiply divided. They are eaten roasted or fried in oil, or cooked with oil and water and condiment, or boiled in only water. (…) And fish that are prepared with water, oil, leeks, dill, and similar are better digested and loosen the belly. Those cooked with vinegar cool more than they moisten. Those that are boiled in water only are the most laudable because their viscosity is taken away in the water they are cooked in, especially if they are eaten with oil, obsomagarum, mint, celery, rue, caraway, pepper, ginger, and similar. (…)
I think cooking fish in a sauce of leeks, dill, and oil actually sounds interesting. I know I enjoyed fish in dill sauce as a child.
Isaac Iudaeus de diaetis universalibus et particularibus, originally written in Arabic in the late ninth or early tenth century, was translated and adapted by Constantinus Africanus in the late 11th century and circulated widely in Italy and beyond soon afterwards. While the original applies to a different context, it is still reasonable to use it as a guide to the advice that Siculo-Normans would have found useful. It is an open question how much the original was altered in translation – I cannot say since I read no Arabic. However, the extensive reference to eating pork suggests that some alterations took place.