Just a few snippets today. We get to more recipe-like things again starting tomorrow.
(…) and to relieve their harm, and if they are very stiptic, it is good to roast them so that their body is rarified. Those that are immersed in warm water temper the dryness of the chest and dissolve difficulty in urinating because their complexion is tempered by the softness and humidity of the water they are suitable to generating good digestive juices. But cholerics eat them with sugar and phlegmatics with honey. (…) p. 417
(…) The oil that is extracted from them is better if their kernels are hard. But if they are first blanched (excorticentur), they should be given to eat as more digestible, more so if they are taken with honey or sugar. (…) p. 434
(…) If they (green walnuts) are eaten on an empty stomach with obsomagarum and vinegar, they moisten the belly, and with rue, they help against poison. (…)
(…) those (ripe walnuts) that are eaten before the meal along with figs defend the body against poison. (…)p. 438
(…) they cause much inflation in the belly, more so if they are eaten with their interior skin on. If they are eaten without that skin, they are more digestible and useful to have against cough, especially if they are eaten pounded with honey. If they are roasted with a little pepper, they quickly relieve the rheumatic and if they are not roasted and eaten on an empty stomach, they help the body against poison. (…)
(…) They are above all others in nourishing their eaters well, but they have a degree of bitterness and sharpness. p. 439
It is basically a list of nuts that are eaten mainly as they are. Though admittedly both sweetened roast chestnuts and hazelnuts pounded to a paste with honey sound attractive. That would basically be hazelnut marzipan. I feel less sure about roasting them with pepper. If you do not fancy the amount of work, Middle Eastern grocers sometimes sell blanched hazelnuts by the bag. It is much fiddlier than with almonds.
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.