In a large heavy-bottomed saucepan or skillet, melt the butter over medium heat.

Add the diced onions and cook until soft and translucent, about 4-5 minutes.

Add the minced garlic and cook for another 30 seconds until fragrant.

If using mushrooms, add them now and cook until they release their moisture and begin to brown, about 5-7 minutes.

Sprinkle the flour over the vegetables and stir continuously for 3-4 minutes to cook out the raw flour taste and create a dark roux.

Slowly whisk in the beef broth, about 1/2 cup at a time, ensuring there are no lumps before adding more.

Add Worcestershire sauce, soy sauce, beef bouillon, tomato paste, thyme, rosemary, bay leaf, onion powder, garlic powder, and black pepper. Stir to combine.

Bring the mixture to a simmer, then reduce heat to maintain a gentle simmer.

Cook uncovered for 15-20 minutes, stirring occasionally, until the gravy has reduced and thickened to your desired consistency.

Remove the bay leaf, taste and adjust seasonings, adding salt if needed.

For an extra silky finish, whisk in 1 tablespoon of cold butter right before serving.

If you'd like a darker color, stir in Kitchen Bouquet or browning sauce.

For a smoother gravy, strain through a fine-mesh sieve before serving. For a thicker gravy, continue simmering to reduce further.