Rub lamb lightly on both sides with Dijon mustard, rosemary and salt and pepper. heat oil in a frying pan on high temperature; add lamb, and sear on both sides until medium rare, approximately 3-4 minutes per side. Serve with a dollop of raspberry blackpeppercorn sauce.
NOTE: Normally canola oil is a better bet for high heat; in this recipe there's enough fat in the lamb to keep the olive oil from burning.
RASPBERRY BLACKPEPPERCORN SAUCE OR COULIS:
Stir ingredients in a saucepan; bring to a boil., Reduce heat and let simmer for 4-5 minutes. Use a whisk to break up raspberries. Make sauce ahead and reheat as needed. Strain sauce to remove seeds, creating a coulis, if people are intolerant of them.