This is an excellent sauce on grilled steak. Look for green peppercorns where capers and pickles are sold in the supermarket. (They're also good in salad dressings.)
Melt 1 tablespoon butter in heavy medium saucepan over medium-high heat. Add shallots and saute until beginning to brown, about 5 minutes. Add peppercorns and mash with back of fork. Add broth, Cognac, and cream and boil until sauce is thick enough to coat spoon, whisking occasionally, about 15 minutes. Set sauce aside.