It really is more like a french onion soup "technique" than anything.
Here's what you'll need:
Onions (if possible different varieties)
broth (chicken, beef or veggie or combo)
Heat oil in a stock pot over medium hugh heat. Cut onions into halves and then cut halves into thin strips. Put the onions in the oil with 1 TB (more or less) of butter. Salt and pepper generously and cook over medium heat stirring often until onions begin to brown. After 25 minutes or so (you may need to reduce heat) onions should be taking on a lovely brown color and be mostly softened and lovely smelling. Add 1 tsp or so of marjoram, stir. Add some chopped fine garlic and cook for maybe 3-5 minutes longer. Then simply deglaze the pan with some broth, scraping the bottom of the pan with a wooden spoon to get up any browned bits. Then add more broth to make soup. Simmer for 15 minutes. Serve by ladling into oven proof bowl, topping with hearty bread and cheese and broiling until cheese is brown and bubbly.
Okay amounts, right? How much broth? How many onions? I'd say six medium onions to a quart container of broth should do it. The onions get pretty small after cooking so add broth till you achieve your preferred onion to broth ratio! I usually use whatever homemade broths I have on hand be they chicken beef or vegetable, and if I don;t have enough of one I will add some of the other. The flavors meld in a nice way during the simmering phase.