Black pepper sauce for steaks is created with peppercorns, cognac and beef broth. Additional ingredients include garlic, shallots and cognac or brandy. The best sauce is made when using the same pan that the steaks were cooked in, which retains a small amount of fat.
Add 1/2 teaspoon of minced garlic and 1/3 cup of minced shallots or onions to the pan. Sauté for a few minutes, then add a heavy splash of cognac or brandy. Scrape the pan to remove stuck-on bits of onion and garlic. Pour in 2 cups of beef broth along with a heavy dash of crushed peppercorns. In another bowl, mix together 1/3 cup heavy cream with 4 teaspoons of cornstarch. Pour into the sauce, and let it simmer until it thickens. Add a squirt or two of dijon mustard to taste, if desired.