Peel and slice the onions.
In a deep large sauce pan, on medium heat, add in the oil and onions.
At the beginning you will only need to stir the onions occasionally, as they start to brown, stir frequently to prevent burning.
This process can take anywhere from 30 to 45 minutes.
Once the onions are a rich brown, add the broth, salt and pepper.
Turn down the heat to a simmer, continue to cook for about 20 to 30 minutes.
Taste and adjust your seasoning.
Preheat the broiler and spoon a serving of soup into a oven proof bowl.
Top the soup with croutons or a slice of bread and sprinkle the cheese of choice over the bread/soup.
Place the bowl into the oven and broil for just a few minutes to a melted golden brown.
Once cheese is melted, remove from the oven and serve.
