Preheat oven to 425 degrees F.
Coat the bottom of the casserole with a little olive oil. Arrange onions in a small casserole (they should just fit without a lot of extra room.) Add the garlic in any empty spaces. Drizzle the remaining oil over the onions. Top with a thin pat of butter. Sprinkle with salt and pepper and add a thin pat of butter on each onion.
Bake for 20 to 25 minutes until the butter/oil is starting to brown. Add wine to a level halfway up the onions.
Continue to bake for another 35 to 40 minutes (about 55 minutes to an hour, total) basting now and then. Watch the level of the liquid as the onions roast, making sure to add a little more liquid if it looks in danger of drying out and/or burning.
When finished, onions should be golden brown, easily pierced with a knife, and the liquid at the bottom reduced to a syrupy sauce.
Keywords: Alcohol, Beef Stock, onions, Wine