Heat a large saute pan over medium-high heat and melt the beef drippings or butter.
Then add in the chopped shallots, carrots, and celery and a pinch of salt and black pepper.
Saute until slightly translucent.
Then add in the chopped garlic and saute for another 2 or 3 minutes.
Whisk in the flour and saute for another 2 minutes, stirring constantly so the flour cooks but doesn’t burn.
Add in the chopped fresh thyme and stir.
Stir in the Worcestershire sauce and continue to stir. Make sure to get all the brown bits scraped off of the bottom of the pan.
Add in the Porcini powder and stir a few times before pouring in the Pu-erh tea concentrate.
Stir continuously for 2 minutes until the sauce begins to thicken.
Then add in the beef stock and bring the sauce to a boil.
Then reduce to a slow simmer uncovered for about 15 minutes.
Once the sauce has reduced and thickened add salt and pepper to taste.
Using a fine mesh strainer, strain out the solids so that you’re left with a rich velvety sauce.
Serve immediately or refrigerate. Sauce will last 3-4 days in the fridge.