Step 1

In a large stock pot or dutch oven, melt the butter and canola oil together over high heat and add the onions. Sauté, stirring occasionally until they start to caramelize, about 15 minutes. Reduce the heat to medium-high and continue to sauté until the onions are a deep brown color, about 1 hour.

Step 2

Deglaze with the sherry and red wine and cook until the liquid is nearly evaporated.

Step 3

Stir in the tomato paste and garlic purée. Add the bouquet garni, chicken stock, and beef base and bring to a simmer and cook for 45 minutes.

Step 4

Skim the butter fat/foamy liquid from the top, and discard. Taste for seasoning and add salt or pepper as desired. Remove the bouquet garni.

Step 5

Ladle the soup into oven-safe bowls and top with 2-3 slices of the baguette, then top with a slice of provolone cheese and grated gruyere if desired. Place the bowls on a baking sheet and broil for 3-4 minutes or until the cheese is melted. Garnish with fresh thyme leaves and serve.