How to Make It
Preheat oven to 450°.
Combine first 4 ingredients in a mini food processor. Add 1 1/2 teaspoons oil; process until finely ground. Sprinkle lamb evenly with salt and pepper; coat with herb mixture. Place lamb in a single layer in a large ovenproof skillet; roast at 450° for 30 minutes, turning after 20 minutes.
Reduce heat to 225° (do not remove lamb).
Cover lamb with foil. Bake an additional 2 1/2 hours or until lamb is tender. Remove lamb from pan; keep warm. Place a zip-top plastic bag inside a 2-cup glass measure or bowl. Pour drippings into bag; let stand 10 minutes (fat will rise to the top). Seal bag, and carefully snip off 1 bottom corner of bag. Drain 1/2 cup drippings into a bowl, stopping before fat layer reaches opening; discard fat. Return the drippings and wine to pan over medium heat; bring to a boil, scraping pan to loosen browned bits. Cook until reduced to 1/2 cup (about 8 minutes). Remove 2 tablespoons wine mixture from pan; stir in flour. Return flour mixture to pan; cook for 2 minutes or until slightly thick. Remove from heat; keep warm.
Combine mustard and 1 1/2 teaspoons oil in a small bowl; brush evenly over lamb. Place mushrooms in a food processor; process until finely ground. Combine ground mushrooms and panko in a shallow dish. Toss panko mixture with remaining 2 tablespoons oil. Press panko mixture evenly over lamb. Place lamb on a broiler pan coated with cooking spray. Broil 4 minutes or until golden brown, turning after 2 minutes. Serve with sauce.