Brush meat with olive oil and toast at 400 degrees F for 20 minutes. Brush on mustard. Mix crumbs or ground nuts with garlic, parsley, rosemary, pepper, and thyme, and gently apply a coating over the mustard by hand. Return to oven and continue to roast at 375 degrees F for 25 to 35 minutes (lamb should be pink inside after about 25 minutes of cooking). Serve with a mustard or garlic hollandaise sauce, if desired.