I can, at least, answer part of your question: how these cuts were cooked.

I see that Essig discusses the Edict of Diocletian which, among other things, set a “price maximum” for numerous goods sold in the Roman world (this is a gross oversimplification, by the way, but I won’t be diving too deep into this topic). As a result, this document gives us a ballpark range of the prices of certain goods. So, this is how we get to Essig’s conclusion that “sow’s udder, sow’s womb, and liver of fig-fattened swine commanded the highest prices of any meat, costing twice as much as lamb” (Essig 69). Unfortunately, I’m not finding any answers as to why this was the case, and so I will not speculate. But we will take the price edict of Diocletian at face value here and assume that this is the case, and that these pig organs were, in fact, the costliest cuts of meat in the later Roman empire.

Now, I can answer your question as to how they were cooked. We have a few recipes as to how wombs and udders were cooked in a text called the De Re Coquinaria (Roughly translating to “On Culinary Matters”), itself being a late Roman recipe text. It is often referred to as “Apicius” after the (wrongfully) attributed author, so I’ll use that name here for the most part.

The first reference comes from the second book of Apicius, which is apparently on “Sarcoptes” (a Greek term, roughly meaning “minced meat”). The recipe for the womb in this case involves stuffing the womb with a forcemeat blend. I’ll provide here Sally Grainger and Christpher Grocock’s translation for this recipe:

Forcemeat stuffing for the womb is made like this: ground pepper and cumin and two small leeks peeled down to the tender parts, rue and liquamen. These are mixed with pieces of meat which have been thoroughly beaten and pounded so that they can then be blended with the spice mix. Add peppercorns and pine nuts, stuff (the mixture) into a well-washed womb; they are cooked like this in water, oil and liquamen, with a bundle of leek and dill. (DRC 2.3.1)

If we are speaking in terms of how it is cooked, unfortunately the Latin is unhelpful here, with a generic verb for cooking, “quocuntur.” However, the reference to cooking it in the broth of water, oil and liquamen tells us that it is likely either being stewed or boiled.

The remaining recipes for wombs (and udders) occur in the seventh book of Apicius, which is named “Politeles” (a Greek term, roughly meaning “expensive”). There are a number of recipes here for wombs, but most of them describe the seasonings to use when cooking them (7.1.1: laser from either Cyrenaica or Parthia, vinegar and liquamen; 7.1.2: pepper, celery seed, dried mint, laser root, honey, vinegar and liquamen; 7.1.3: pepper, liquamen and Parthian laser; 7.1.4: pepper, liquamen and spiced wine). Recipe 7.1.6 gives us a slightly better understanding of how to actually cook the womb, telling us to coat the womb in bran and cook it in a brine. The word used here for brine is “muria,” which is also used to describe the heavily salted liquid used for pickling.

Immediately following the womb recipes, we have two udder recipes. The first is boiled and given a sauce of pepper, lovage, liquamen, pure wine and passum, thickened with starch (7.2.1). The second is not unlike the first womb recipe in that it is stuffed. The contents, however, are far more luxurious. I’ll again provide the translation from Grainger and Grocock’s edition:

Full (stuffed) udder: pepper, caraway and salted sea-urchins are ground (and stuffed inside); it is sewn up and cooked like this. It is eaten with allec and mustard. (DRC 7.2.2)

So, wombs and udders were really prepared in a variety of ways. While often stuffed, we also have instances of them being cooked without any mention of a stuffing. I will, however, point out that each mention to a cooking method in these recipes always describes some sort of boiling process.

I hope this was helpful!