Put the PR in a pan on a rack with 2 cups of beef stock 1 stalk of celery 1 carrot cut into 3-4 pieces and a 1/4ed onion when you take the PR off the pit add 1/2 cup of merlot to the stock and reduce by 1/2 add 2 tbl butter and whisk hell out of it.
Bludawgs recipe and method is a good one. I would use more beef stock, as I find jus goes fast. I prefer Merlot or Malbec as well. Salt and pepper to taste. Oh, I also put a small head of garlic, cut in half in the roasting pan
Take the usually minuscule amount of renderings you will get from a PR and add beef stock, some Worcestershire, a little red wine, garlic powder, salt, and pepper, bring to a good rolling boil to reduce it and viola.
It is pretty amazing that what I do is so similar to the above. I take the foil pan that my roast cooked in and put on the cooktop. Add 32Oz + unsalted beef stock and heat till I can get all the dried drippings melted. Then I add whatever big wine I have open, Cab, Zin, Merlot all good. Add some minced garlic and cook for awhile. Then add salt and pepper to taste.
Man... My au jus was completely HORRIBLE! Straight up poured it into the sink. Added too much worcestershire and it ended up tasting sour... Meh... I made horseradish cream instead. But up to that point I had onions, carrots, garlic, and mushrooms in the pan throughout the cook with salt free beef stock. It would have been fine if I didnt go crazy with the worsty...