This was created after trying a number of different types of onion soup recipes. It makes a large pot of a very satisfying comfort food. Goes great with grilled cheese, or just a good loaf of crusty bread.
Melt the butter over medium high heat in a dutch oven. Fry the bacon until crispy. Remove with a slotted spoon to paper towel and set aside.
To the bacon drippings add the yellow, red, and white onions, shallots, thyme, bay leaf, salt and pepper. Saute, stirring often, until the onions begin to caramelize (at least 15 minutes).
Add the leeks and continue to cook for 5 minutes.
Sprinkle on the flour, and stir gently until all the flour is incorporated. Continue cooking, stirring often, until the flour has begun to cook (at least 5 minutes).
Add the Chicken stock and taste to adjust seasonings. Bring to a boil, scraping up any browned bits off the bottom. Once boiling, reduce the heat to low and simmer, partly covered, for 45 minutes, stirring occasionally.
Remove the bay leaf and use a submersible blender to puree the soup. Add the cream, taste to adjust seasonings, and simmer for an additional 10 minutes.
Ladle into individual bowls, sprinkled with some of the reserved bacon.