Okay, squick question from someone with very limited ars experience...
situation is.. magus has piece of meat ( I think Lamb), anyway, magus wants to cook said meat using magic.. now question.. would appropriate technique be creo and thus used to "improve" the raw meat to cooked.. or rego as is done for craft skills? Any clarification would be appreciated.. its probably pretty obvious for most folks.. but I've had limited experience. especially lately
I think it would be Rego Animal, as per the rules in Rego Craft Magic (see "Covenfolk Spells"). It would be Base 3,
"Treat and process items made of animal products", with possibly a Creo Herbam requisite (and +1 magnitude) if you want it spiced (or a low level Muto Imagonem spell after that to make it taste as you want). And a Precision roll not to spoil the meat .
So the final level would be: 3 + 1 Touch for a spell of level 4. And then a precision roll of 6+ to make it edible, or 9+ to make it acceptable. Of course the "change" would be permanent (duration momentary). Sorry if i haven´t enough time to make it flavorful .
Marciano got it right THe imaginem spell to follow (as he suggested would be base 2 (change smell and taste), +1 touch +2 sun for a level 5 spell. Or you can do it with 2 level 4 spells (one to affect taste, another to affect smell).
Other ways to "skin the cat" would be creo ignem to actually roast it or Creo Aquam to boil it (ignem requisite for hot water).
Nitpicking: If you have the herbs, it's just a Herbam requisite and the meal can be eaten even with parma up. If you have to create the spices, it would be two requisites (Creo and Herbam) and you would not be able to eat it with parma up (a single Muto requisite to change the taste would also do the trick, though Parma remains a problem). With MuIm you do not even have to bother cooking the meat in the first place (see Taste of Herbs and Spices, MuIm 5) and Parma is not an issue, since the species are non-magical.
Note that raw meat tastes "bad" in the medieval mindset, but it's not unhealthy per se (after all, all meat-eating animals eat it raw). So it's no problem masking it with an illusion. For the same reason, processed meat is not closer to the platonic idea of meat than raw meat (in fact, it's arguably further), so Creo cannot be used to "improve" it.
My first reaction would be to say: for the same reason why, if you take a pot, and cup of dry lentils and you use Creo Aquam (Ignem) to create boiling water in which to cook them, once the spell expires your lentils will be dry and not juicy
Admittedly, this is less obvious than I first thought, and not having read A&A my understanding of Ars Magica physics is limited. In fact, re-reading my Aristotle , I am starting to think that it might work the way you say, and that the magically created fire would elicit a change in the meat, making it non-magically hot.
On the other hand, I think that if this was the proper interpretation, then creating a magical sling and using it to hurl a non-magical rock would allow both the rock and its "motion" bypass parma. Which I believe it's not the case; it seems that in chain of physical causes (A heats B, which then heats C etc.) even if only the first element of the chain is magical, then Parma can block any element of the chain. This is in accordance with Aristotle's views that the properties of the chain stem from those of the first element.
The effects of the spell remain once it ends. Otherwise a pilum of fire would burn you... and then you would be totally healthy once the Momentary duration ended. The lentils you mentioned would be cooked, but dehydrated (water disappears, but not its effects). It is in the section on Hermetic magic, if I recall correctly
Indeed; the question is, however, whether they are cooked and cold or cooked and hot. Because it's not clear if the Ignem you create "seeps into" the lentils just like water (in which case it disappears at the end of the spell, leaving them cold), or creates a natural change in the lentils (from cold lentils to hot lentils) which remains after the spell ends.
After some thought, I would argue for the first position: when you make something hot, you are adding Ignem to it, not eliciting a natural change in the object. The reason is that to make something hot, you use Creo Ignem, not Muto. So, the reason that your cooked lamb and/or lentils are hot is not that they have changed, but that they contain Ignem - magical Ignem, which either you placed directly into them, or that you placed nearby and "soaked" them.
Can you point out one or three? I can't find any. Remember, one thing is to be cooked/burnt, one thing is to be hot.
Ignem can elicit natural changes in an object - melting it, burning it, cooking it etc. Those remain after magical Ignem is applied to the object. But the Ignem itself - including the heat that soaks the object - is magical, is resisted by Parma, and disappears at the end of the spell.
Would they be dehydrated? The lentils have changed into a form which contains water, yes, but that's a modern view. Have they not changed to a form where their properties are more hot and wet than cold and dry, neither of which actually require water to be present at all?
From the top of my head, check the Creo Ignem section. IIRC there are at least 2 spells that leave the item red-hot even once the spell ends. Others leave the item burning naturally once the spell ends. The magic goes out, but its ffects remain. A metal cooking pot is totally oblivious to the fact that it has been heated over a CrIg fire (or with a CrIg(Te) spell) or a natural bonfire: it will remain hot and cook its contents. That is how we have always applied it IMS. Serf's Parma, since my books are some 400 km away, but hey
According to this interpretation, it would be easy to create "natural", drinkable water simply by creating magical water, drenching a natural piece of cloth, and then squeezing "out" of the piece of cloth perfectly non-magical water. And if you are hungry, you can try it with soup!
It kind of feels ... wrong to me, but I'm really enjoying this discussion - it's quite enlightening.