Preheat the oven to 475 degrees F. Use a paring knife to cut several deep slits into the roast. Push the garlic slices into those slits. Place the roast in a small roasting pan. Brush with the mustard and sprinkle with herbes de Provence, salt and pepper. Roast for 10 minutes. Reduce the heat to 325 degrees F and roast 35 minutes more. This should yield a rare to medium-rare roast. If you like your beef medium to medium-well, cook 10 to 15 minutes longer. Transfer the roast to a plate and allow it to rest for 10 minutes before slicing it thinly. To make a jus to serve with the beef, set the roasting pan on the stovetop over medium-high heat. Add the stock and bring to a simmer, scrapping the bottom of the pan to release the tasty brown bits on the bottom.