Step 1
Process bread cubes, mushrooms, and tarragon in a food processor until finely chopped, about 20 seconds.
Step 2
Stir together mustard, salt, and pepper in a small bowl. Coat roast with mustard mixture until evenly coated. Sprinkle all over with breadcrumb mixture, pressing to adhere. Place roast on a baking sheet, and chill, uncovered, at least 4 hours or up to 8 hours. Let roast stand at room temperature 1 hour before cooking.
Step 3
Fill a pellet container to an electric pellet grill with hardwood pellets according to manufacturer’s instructions. Set temperature to 350°F, close lid, and preheat pellet grill 10 to 15 minutes.
Step 4
Place beef on oiled grill grate, fat cap side up, close lid, and grill until a meat thermometer inserted into thickest portion registers 120°F, about 2 hours and 15 minutes. Transfer roast to a cutting board, cover with aluminum foil, and let rest 20 minutes before slicing. (Internal temperature will continue to rise to medium-rare.) Serve sliced beef with any accumulated juices on cutting board. |