Here is my basic jus recipe. Minus the use of base.
Drippings including fat from brisket wrapping
cut offs from brisket (I use the ones from previous cooks, but, it can be that days cook)
enough water to make 2 cups total of liquid
1 tablespoon fish sauce or Worcestershire sauce
Bring all ingredients to boil for 5 minutes, mash cutoff to infuse into liquid. You are looking for a salty, smoky liquid here. Strain and reserve for step 2.
4 tablespoons of finely chopped onions
1 teaspoon of finely chopped garlic*
1 tablespoon of rub or equal parts chile powder, granulated garlic, black pepper
Saute onions and rub, add garlic to soften. Once onion and garlic are softened, add in liquid from prior step. Bring to simmer for 5 minutes to combine flavors.
* for garlic, I normally do not use a knife to mince garlic. I will smash the garlic slightly, add some kosher salt and then using a pastry cutter, cut the salt into the garlic, this gives a much better flavor.
** yes, I save my cutoffs from each cook, be it pork, ribs or brisket, when I need to make a jus or sauce, I start my base liquid by boiling these things to create a flavorful meat base. You can even reduce it by 3/4, and get a demi-glace like version of liquid smoke without the chemical flavor.