1 (5 to 6 pound) boneless top sirloin roast
kosher salt and freshly ground black pepper
2 T. vegetable oil
1 c. coarse fresh baguette bread crumbs
4 cloves garlic, minced
2 medium shallots, minced
1 T. roughly chopped thyme
1 T. roughly chopped marjoram
3 T. melted unsalted butter
1/3 c. Dijon mustard
Creamy Horseradish-Mustard Sauce
1 c. Creme fraiche or sour cream
3 T. prepared horseradish
3 T. Dijon mustard
1/2 t. kosher salt
Let roast sit at room temperature for 30 minutes. Position a rack in the middle of the oven and heat to 400º. Line a roasting pan or rimmed baking sheet with foil.
Season roast liberally with salt and pepper on all sides. Heat the oil in a large saute pan over medium-high heat. When the oil is hot, brown the meat well on all sides, including the ends. Transfer the meat to the roasting pan. Set aside to cool white you prepare the crust.
In a medium bowl, combine the breadcrumbs, garlic, shallots, thyme, marjoram, 1/2 t. salt, and 1/4 t. pepper. Pour the melted butter into the breadcrumb mixture; toss to combine. Using a rubber spatula, smear the top and sides of the beef with the mustard. With your hands, lightly press the breadcrumb mixture into the mustard.
Roast the been until an instant-read thermometer inserted into the thickest part of the meat reads
125º for medium rare, about 60 to 80 minutes. To keep from over-browning, check the roast after 30 minutes of cooking and when the crust is golden brown, tent it with aluminum foil.
Make the horseradish-mustard sauce.
Remove the roast from the oven add let the meat rest for 10 to 20 minutes before carving, across the grain, into 1/2 inch slices.