Tenderloin Roast with Zinfandel Sauce

I was given a Bluetooth-enabled temperature monitor called the iGrill last year, and it is fabulous. It works like a meat thermometer, but it Bluetooths the temperature out to an app on your phone, and you see a plot of the rising temperature as it cooks. You can set a goal temperature (such as 120 F) and your phone will tell you when you're done. This is invaluable if you're distracted at a dinner party. For this recipe, use the highest quality beef tenderloin you can find, and use a decent Zinfandel (red!) wine, which should have some jammy notes of blackberry. I like "7 Deadly Zins" for this sauce. Also watch the salt that can come from the stocks. It's better to use unsalted stocks and adjust the salt yourself than have too much.

4 large shallots, peeled and sliced thin
a little peanut oil
dried Chanterelle mushrooms, soaked in hot water 30 minutes
2 Tbsp raspberry wine vinegar or red wine vinegar
2 Tbsp sugar
1 bottle good Zinfandel with black fruit notes
2 cups beef stock (low salt)
2 cups chicken stock (low salt)
Fresh thyme sprigs
Black peppercorns
Bay leaf
2 Tbsp flour
2 Tbsp butter, softened
1 two-pound (1 kg) boneless beef tenderloin
salt and pepper
fat for searing the beef (pork fat, butter, peanut oil, etc.)

Reconstitute the dried Chanterelles with hot water, soaking for 30 minutes. Drain. Heat a large saucepan and add some oil. When the oil is hot, add the sliced shallots and the mushrooms. Cook until the shallots are tender and translucent. Add the vinegar and the sugar. Cook until the liquid disappears and the mixture is dark and fragrant. Add wine and boil until the volume is halved. Add both stocks, thyme, a dozen peppercorns, and a bay leaf. Bring to boil, reduce to simmer. Simmer uncovered for at least 30 minutes and up to an hour or more. Strain sauce through a fine sieve or cheesecloth into a small saucepan. Bring back to a slow simmer. Thicken by making a beurre manie: mix together the butter and flour using a fork, and add the mixture a piece at a time to the simmering sauce, whisking well after each addition. If the sauce is too thin, make a little more manie and whisk it in. Bring back to the simmer. To keep the sauce, either pour into a Thermos until service or keep it off the heat and reheat gently for service.
To make the beef, preheat the oven to 350 F. Season the beef well with pepper and especially salt on all surfaces. Heat a large oven-proof skillet over high heat and add fat or oil. When the fat is hot, add tenderloin and sear well on all sides. As you turn the meat onto the final side, insert a meat thermometer and place in the oven. Cook to an internal temperature of 120 F for medium-rare. Remove the beef and place on a cutting board, tenting with foil, to allow to rest. Rest for about 10 minutes. Carve the beef into thick slices and serve with the warm sauce over or on the side.