Original recipes from De honesta voluptate:

On Onions. The odor of all kinds produces tears, though the Tusculan onion is less strong, really almost sweet. Red onions are sharper than white, dry than green raw than cooked, and dry than seasonsed.... About onions, doctors agree for the most part that inflammations are clearly kindled by them, the head made to ache, brain and memory impaired, deep sleep induced, phlegmatic humours sometimes generated and other times removed. Some, however, think they are healthful when used moderately because they soften the bowels, induce dreams, create appetite, especially arouse sexual appetite, and increase its foment with lustful dampness. (Milham, 185, 187)

On the Seasoning of Onions. Onion is also cooked under ash and cinders until it has breathed out all rawness. When it has cooled, it is cut up in bits, put on a plate and rolled in salt, oil, and condensed must, or must. Some even sprinkle on pepper or cinnamon on onion. (Milham, 227)

Modern recipe: Baked and Roasted Onions

For 160:

• 160 whole onions, skin removed, sliced 1/2" thick 
• 1 1/4 quarts olive oil
• 1 1/4 quarts balsamic vinegar
• 1 1/4 quarts water
• 5/8 quart fresh rosemary, chopped 
• salt and pepper to taste

• 8 whole onions, skin removed, sliced 1/2" thick
• 1/4 cup olive oil 
• 1/4 cup balsamic vinegar
• 1/4 cup water 
• 2 tablespoons fresh rosemary, chopped
• salt and pepper to taste 

Per serving nutritional information:

2 Calories; 7g Fat (66% calories from fat); 1g rotein; 7g Carbohydrate; 0mg Cholesterol; 550mg Sodium

Notes on the recipe:

Platina makes no mention of how the outside of the onion should be treated. Should the onion be peeled prior to roasting or after? From experimentation, peeling after roasting seems to preserve the most onion flesh to be cut into bits, but ultimately we can't be certain. Regardless, onions were placed whole under the ashes and cinders of a fire and left to cook until the raw nature of the meat left the onion. Upon removal from the ashes they were possibly peeled, cut in bits, rolled in salt and oil and must, and possible sprinkles with pepper or cinnamon. Elsewhere in his manuscript, Platina suggests that onions may be seasoned with other spices as well, but no evidence is given of spicing in this recipe and so the cook is left to their own creativity.

It is interesting to read Platina's distinction between various onion types, specifically his mention of red and white onions. More interesting to us was his mention of onion varieties that border on sweet, similar to the Maui, Walla Walla, Vidalia, Texas 1015s or California Imperial Valley marketed today. Presumably many of these varieties could be substituted if necessary, though research into the actual varietal soil contents near Platina's home would probably be most telling in attempting a comparison to modern sweet onions. If similar soil types could be found where one of the sweet American varieties is grown, that substitution would seem to be the best choice given the possibly inaccessible original.

Whole or chopped prior to cooking:

We did not bake the onions whole and chop them when cooked through as the original recipe suggests. Instead, we chose to save time and make use of an abundance of ovens at the feast site. For this reason, the instructions for making this dish suggest chopping and then alternately steaming and roasting the onions to cook them. If you wish to cook the onions whole, we suggest planning extra time into the cooking schedule. Baked onions hold heat for a very long time. You will need the extra time in your schedule to wait for the onions to cool to a level safe for handling. You can speed this process by peeling the onions prior to baking them. Preserve more of the flesh by wrapping each onion in aluminum foil before baking (much like you might bake a potato).

Avoiding tears during chopping:

Any number of suggestions will be given to people attempting to avoid the inevitable tears that result from chopping onions, some more fanciful than others. Your tears are the result of an onion's attempt to protect itself. Chopping releases gasses from the onion's flesh which, when combined with human tears, results in the formation of sulfuric acid. We find that none of the fanciful measures for avoiding tears work (including bread on the head and potato in the mouth). However, all hope is not lost. Some people have used the following techniques with greater measures of success:

• Cool the onions overnight prior to chopping (do not freeze them) to reduce the production of onion gas and thus acidic tears
• Use a food processor to speed chopping and reduce the time spent near the onions
• Wear clear plastic swimming goggles (which may make you look foolish, but form an airtight seal around the eye) during chopping, being sure to air the room prior to removing the goggles
• Find someone whose tears do not react with onion gasses (yes, these people do exist).

Milham, Mary Ella. Platina's On Right Pleasure and Good Health. University of North Carolina at Asheville: Pegasus Press, 1999. ISBN: 0866982086.