For the beef: The day or night before you are going to cook and serve the roast, unwrap the beef, dry it off with a piece of paper towel and place onto a small baking sheet or roasting pan lined with a wire rack. For easier cleanup, line the pan with aluminum foil. Return the roast to the fridge and allow it to sit uncovered for at least 8 hours. This process will greatly increase the roast’s browning potential and help the flavourful butter stick to the outside.
Remove the roast from the fridge and place it on the counter for at least 2 hours or up to 4 hours to come up to room temperature.
Preheat your oven to 500 F and, once heated, set a timer for 30 minutes. With the oven sear method, you want your oven to be smoking hot, and allowing it to sit at temperature for half an hour will help ensure a good golden-brown colour.
Meanwhile, in a small bowl, combine the butter and herbes de Provence. Spread the butter all over the roast and season well with salt and pepper. If using a digital probe thermometer (and I do highly recommend using one), insert it into the center of the roast, avoiding the rib bones if using a bone-in roast, and set the temperature alarm for 130 F. Transfer the roast to the oven and set a timer for 20 minutes for a 4-lb roast. When the timer goes off, turn the oven off and set another timer for 2 hours. Without opening the oven door, allow the roast to sit in the oven for the full 2 hours, or until the probe thermometer reaches 130 F.
In the last 30 minutes of roasting, prepare the sauce.
Place the bacon in a large skillet set over medium heat and cook until crisp, about 5 minutes. Remove the bacon to a plate, leaving the fat behind, and add the mushrooms. Season with salt and pepper and cook until lightly golden, about 5 minutes, stirring occasionally.
Add the thyme and cocktail onions, and continue to cook until the mushrooms are golden brown and the onions pick up a little colour, about another 5 minutes. Add the garlic and cook for 30 seconds, then transfer the mushroom mixture to the plate with the bacon and set aside.
Place the pan back over medium heat, melt in the butter and sprinkle in the flour. Whisk together, then add the tomato paste and cook for about 1 minute. While whisking, slowly pour in the wine followed by the beef broth. Bring the mixture to a simmer and cook for 5 minutes to thicken slightly. Add the sugar as well as the mushrooms, onions and bacon to the sauce and simmer for 2 to 3 minutes to thicken and heat through. Season to taste with salt and pepper, stir in the parsley and turn the heat down to low to keep warm.
When the timer or thermometer goes off, remove the roast from the oven. Cut off the ribs, if using a bone-in roast, and slice. Like with a reverse-sear method, this oven-off cooking method does not require resting the roast before serving. Serve the roast topped with the bourguignon sauce.