Preheat oven to 325°F. Line a shallow roasting pan with foil. Place a rack on top of the foil.
Using a pastry brush, brush 6 tablespoons mustard all over the top round roast.
In a small bowl, combine the thyme, salt and pepper; mix well. Sprinkle seasoning completely over the roast.
Arrange roast on prepared roasting pan. Bake, 1-¼ to 1-¾ hours or until an instant-read thermometer inserted horizontally in the thickest part of the roast registers 145°F for medium-rare or 160°F for medium (see tip).
Remove roast from oven and tent with foil. Let rest 5 to 10 minutes.
Shallot Sauce
Meanwhile in a small skillet over medium-low heat, heat oil until shimmering. Add shallots and cook, stirring often, 3 minutes. Add the thyme and cook, stirring 2 minutes or until shallots are softened and golden. Set aside.
In a medium bowl, combine sour cream and mustard. Stir in shallots.
Slice roast across the grain into thin slices. Season to taste with salt.
Arrange beef slices on a platter. Serve with mustard mixture alongside.
Notes
The meat will continue to rise in temperature 5 to 10 degrees while it is resting. For this reason, I recommend taking your roast out of the oven before it reaches the ideal temperature. The USDA recommended temperatures for beef are 145°F for medium-rare and 160°F for medium.
10 medium shallots will yield approximately â…” cup minced shallots. If you end up with slightly more or less, that will be fine in this recipe.
Fresh uncooked top round roast can be refrigerated for up to 5 days and frozen for 4 to 12 months.
Cooked top round roast can be refrigerated 2 to 3 days and frozen for 2 to 3 months.