Presenting lamb in this elegant fashion is a sure crowd pleaser. Keep in mind that the size of the roast will affect its roasting time, and be sure to have the meat at room temperature when you begin.
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.