How to Make It
Cook roast: Pat dry, then season generously with salt and pepper. "The bigger the piece of meat, the harder it is to overseason, so go crazy on the salt and pepper." Heat a large cast-iron skillet or dutch oven over medium-high heat. Swirl in oil and sear roast, turning every few minutes, until evenly browned all over, about 15 minutes. Transfer to a plate. Add thyme, garlic, and butter to pot and cook, stirring occasionally, until butter foams up and garlic is lightly toasted, about 2 minutes. Pour seasonings over roast. "This gives the butter a chance to cool before it goes with the roast into the bag. Otherwise it'll melt the bag."
Meanwhile, using a sous vide circulator and following its instructions, heat a large pot of water to 133° for medium-rare with a tender, steaklike texture. Set the time for anywhere from 18 to 24 hours. "Once the meat is done, it holds for a remarkable length of time without compromising the results."
Add meat and seasonings to a 2-gallon resealable plastic freezer bag. "Use a brand name like Ziploc or Glad, and use the heavy-duty freezer type. They're 100 percent polyethelene and totally inert--no funny chemicals." Fold top into a cuff--"it keeps the seal cleaner." Lower bag into water, opened, just until meat is submerged but opening is above water. If bag floats, drizzle in a few tablespoons of olive oil. "It'll expel the air trapped in the herbs, and that helps the meat sink." Seal bag and clip to side of pot with a clothespin. Cook meat sous vide overnight at your chosen temperature and time. If cooking at the higher temperature, loosely cover pot with plastic wrap to keep water from evaporating.
Make sauce: Peel onion and carrots. Put peels in a wide medium pot, then dice onion and carrots into 1/2-in. cubes. Stem mushrooms (add stems to pot) and cut into quarters. Mince chives and chop parsley (add stems to pot), then put on a plate and cover with a damp paper towel.
Add 2 tbsp. oil to sauce pot. Cook peelings over medium-high heat until softened, stirring often, 5 to 10 minutes. Lift bag out of sous vide pot and, keeping roast in bag, carefully pour juices and seasonings into sauce pot; return roast in bag to water to keep warm. Cook peelings, stirring occasionally to scrape up browned bits, until juices evaporate, about 20 minutes. "You want to reduce the juices until they start to fry. Then you're browning the proteins and really making flavor. Also, it makes a clean, glossy sauce." Add wine, thyme, and some pepper and cook until reduced to 1/4 cup, about 15 minutes.
Strain sauce into a bowl and discard trimmings. Pour sauce back into pot and add demi-glace and 1 1/4 cups water. "The demi-glace adds texture and umami, and also makes more sauce." Bring to a boil, whisking to dissolve. If you want to use gelatin for a classic, stick-to-your-lips texture, spoon a few tablespoons of sauce into a small bowl, sprinkle in gelatin, and stir to dissolve; then stir back into sauce. Season with salt to taste and stir in 2 tbsp. butter. Cover and keep warm over very low heat.
Cook vegetables: Add bacon to a large, deep frying pan and cook over medium heat until it begins to brown. Add carrots, a pinch of salt, and about 2 tbsp. water "so they don't scorch. I'm going for fresh, sweet, slightly crunchy steamed vegetables rather than browned ones, because the meat and sauce are so rich." Cover and cook over medium-high heat until lid is hot to the touch, which means the food is steaming; then cook until carrots are just tender, about 2 minutes more. Add onions, cover again, and cook until barely softened, about 1 minute. Add mushrooms and remaining 2 tbsp. butter, cover, and remove from heat (they'll keep cooking off the heat).
To serve: Remove chuck roast from bag, set on a cutting board, and snip off twine with scissors. Sprinkle half of minced herbs on board and roll roast in herbs to cover evenly. Cut roast into 1/2-in.-thick "steaks."
Sprinkle remaining herbs into vegetables along with a small splash of oil and salt and pepper to taste. Mix gently, then spoon a portion into each of 4 to 6 wide shallow bowls. Set a steak in each and serve with sauce on the side.
*Try to get a roast from the rib end of a full chuck roast--it will be more tender. You can have this cut at a meat counter.