Instructions

1. In a medium saucepan, melt the unsalted butter over medium heat until it bubbles and is completely melted.
2. Add the finely chopped onion and minced garlic to the melted butter. Sauté for about 5 minutes, or until the onion becomes translucent and the garlic is fragrant, stirring occasionally to prevent burning.
3. Sprinkle the all-purpose flour over the onion and garlic mixture. Stir well to combine and cook for an additional 2 minutes, allowing the flour to cook off its raw taste and develop a nutty aroma.
4. Gradually pour in the beef or chicken broth while stirring constantly to prevent lumps from forming. Continue stirring until the mixture is smooth and well combined.
5. Add the Worcestershire sauce and Dijon mustard, then season with salt and black pepper to taste. Stir well to ensure all ingredients are fully combined.
6. Bring the sauce to a gentle simmer and let it cook for about 20 minutes, stirring occasionally. The sauce should thicken to your desired consistency; if it's too thick, you can add a bit more broth to reach your preferred texture.
7. Taste the sauce and adjust the seasoning if needed, adding more salt or pepper according to your preference.
8. Remove the saucepan from heat and allow the sauce to cool slightly before serving. The sauce can be stored in an airtight container in the refrigerator for up to one week.