Add 6 tablespoons of unsalted butter to a medium or large saucepan and melt over medium-low heat.Once melted, add the chopped onion.Mix the butter and onions until the onions are fully covered in butter.
Saute the onion for 1-2 hours.Remember, you must cook on medium-low heat so that the onion doesn’t burn.Tip: Set a timer on your phone for 20-minute intervals. At each of those intervals, stir your onions.
First, increase heat from medium-low heat to medium heat.Next, add 3 tablespoons of flour to the caramelized onions, a little bit at a time.Using a wooden spoon or a wire whisky, fully dissolve the flour into the butter.Next, add a 1/2 teaspoon of salt and mix thoroughly.Stir occasionally for 5-10 minutes until the roux is deep golden brown in color.
Add the 2-1/2 cups of chicken stock to the roux. Feel free to use your own broth if you have any on hand. (You would create your own chicken broth by mixing chicken bouillon with water).Bring to a simmer, stirring occasionally. Once the “giblet broth” starts to thicken, take it off the heat.
Purée using an immersion blender until consistency is silky smooth. You can use a regular blender, but use caution as the heated liquid expands in the blender, so if you overfill, it can cause the lid to pop off.
Once you’ve reached your desired consistency, taste the gravy and adjust seasoning. You can add a splash of sherry vinegar or lemon juice to cut the richness a bit (by increasing the acidity) or add a tiny pinch of cayenne pepper to make it pop.