We are still not done with Ishaq b Sulaiman al-Israili
(…) There are two kinds of fires: One is for roasting and baking (panificandum), the other is for boiling and cooking in vessels (elixandum et coquendum). As to the the fire for roasting and baking, it is good if it were gentle and quiet, without flame, and temperate in heat. (Even?) so that it does not prevail over the exterior of the body, consuming its humidity and dry and harden it before the interior is cooked. If the foods to be roasted do not have laudable humidity, they must be long placed by the fire so that their humidity is consumed and dried out.
But the fire to boil or cook must be hotter because the water in which the foods are cooked opposes the action of the fire. It should not have many flames, but be close to the coals. It is more laudable for a fire to have many coals because their power to heat is stable (aequalis) as their action acts equally in all foods to be cooked and in all their parts. Flames are unlike this, as they rise sharply and needle like (?pineata) and it does not reach every vessel equally everywhere. Hence the cooking of the foods is not equal.
The purpose of water is twofold: It softens dry foods such as beans and other legumes that are submerged in water so that they become softer to eat. And if they have a grave and bitter flavour, they lose their bitterness, such as lupins and similar foods that are immersed in water because they acquire sweetness from it.
The purpose of salt is fourfold: It makes subtle and tempers gross and viscous foods such as fish and their like. It gives savour to insipid foods such as gourds and similar. It dries out humid foods and removes the heaviness of the odor from bad-smelling ones. It is good to add more salt to gross and fatty foods than to others.
Cap. Lxiii of vinegar
The purpose of vinegar is twofold: It removes the abominableness of foods that are abominable and corrupt the stomach and renders them flavourful and strengthening to the stomach. And it makes foods subtle without cooking. That is why it is sometimes found in ptisana; we add a little vinegar so that it helps its subtleness without heat.
Cap lxiiii of oil
The purpose of oil is threefold: It contributes to the taste of foods. To those in which dryness predominates, it gives softness and gentleness, as with millet, lentils and others. It gives its viscosity to sharp and biting foods and tempers their sharpness and bite.
Fire management and basic ingredients. No recipes this time, just for the sake of completeness, and to illustrate there’s nothing primitive about open fire cooking
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.