Step 1

Rinse mushrooms and pat dry. Break off mushroom stems. Set mushroom caps aside. Roughly chop mushroom stems and onion separately. Finely chop shallot and set aside.

Step 2

Heat oil in a medium saucepan over medium heat. Add onion and saute until softened and lightly browned, about 5 minutes.

Step 3

Add mushroom stems and saute until lightly browned, 3-5 minutes.

Step 4

Add tomato paste and cook, stirring and scraping, to concentrate the flavors slightly, 1-2 minutes. Add sugar and red pepper flakes; cook another 1 minute, reducing heat to medium-low if bits sticking to pan start to get dark.

Step 5

Add red wine and balsamic vinegar, and scrape up browned bits. Adjust heat as needed to maintain a gentle simmer and cook uncovered until liquid is reduced to 1 to 1 1/4 cups, 20-30 minutes.

Step 6

Choose a red wine with soft tannins and not a lot of oak, which can make your sauce slightly bitter. A good affordable choice is gamay or Côtes du Rhône.

Step 7

In another medium saucepan, melt butter over medium heat, then add flour and whisk to make a smooth paste. Cook, whisking frequently, until paste is pale gold and smells lightly toasted, about 2 minutes.

Step 8

Whisk the beef broth and red wine reduction into saucepan and continue simmering, whisking occasionally, until sauce has thickened and reduced to about 2 cups, another 30-40 minutes. The flavor should be nicely concentrated.

Step 9

Meanwhile, slice cremini mushroom caps very thin.

Step 10

If mushrooms are large, cut in half first, and then cut across into thin slices.

Step 11

Heat butter in a large frying pan over medium heat. Add reserved shallot and saute until soft and fragrant, about 3 minutes.

Step 12

Add sliced cremini caps and saute, stirring and scraping frequently, until mushrooms are tender and juices are brown and start to stick to pan, about 15 minutes. Be sure to scrape the pan as mushroom juices form.

Step 13

To add more complex flavor, add 4 oz. fresh maitake mushrooms (also called hen of of the woods), chopped.

Step 14

Pour a little red wine sauce into mushrooms and stir to loosen any browned bits, then scrape mushroom mixture into red wine sauce.

Step 15

Whisk in the Worcestershire, Parmesan, and butter. Season to taste with salt and pepper. Set aside, or refrigerate up to 3 days.

Step 16

Preheat oven to 275°F.

Step 17

Slow-roasting is a double win here. The beef cooks more evenly than it would at a higher temperature, allowing the whole roast to reach medium-rare, rather than having a rare center and well-done outer ring. Cooking at a lower temperature is also forgiving, allowing the cook some leeway since the roast won’t go from rare to overcooked in just a few minutes.

Step 18

If beef tenderloin isn't already trimmed, use a chef's knife to carefully cut off fat and silver skin. (Silver skin is the shiny connective tissue that runs the length of much of the meat.) Cut garlic into very thin slices. With a sharp paring knife, cut a slit into beef and slide in a garlic slice. Be sure slit is deep enough to accommodate the whole slice. Repeat to distribute garlic evenly over tenderloin.

Step 19

Rub tenderloin all over with kosher salt.

Step 20

If the beef is not yet tied, cut 8 to 12 pieces of kitchen twine long enough to wrap around the meat. Tie meat with the twine at even intervals, tight enough to help meat hold its shape.

Step 21

Rub roast with oil, season with pepper, and then tuck thyme and rosemary sprigs into twine, evenly distributing them all over the roast. Arrange roast on sheet pan.

Step 22

Roast meat until medium-rare (the thickest part of roast should read 135°F on an instant-read thermometer), about 1 hour.

Step 23

Check to see that meat is done. Remove from oven or add time as needed.

Step 24

Let roast sit 10 minutes. Gently reheat Red-Wine Mushroom Sauce. Snip kitchen twine from beef and remove. Slice beef and set on a platter. Scatter parsley on top and serve with sauce on the side.