In a large skillet, melt the butter over very low heat (otherwise it may burn). Cut the butter into small pieces and stir constantly with a wooden spoon.

Once the butter is melted, add the cornstarch (used to thicken the sauce). Stir constantly over low heat. Cook for about 3 minutes.

At the same time, in a separate saucepan, heat the water and add the beef bouillon concentrate to dissolve it. (If you have homemade beef broth, you can use that instead.) Once dissolved, set aside.

Add the green peppercorns to the butter and cook for about 1 minute. Then pour in the heavy cream and the beef broth, stirring constantly with a wooden spoon over medium-low heat until the sauce thickens.

Meanwhile, in another small saucepan, heat the brandy or cognac over medium-high heat and carefully ignite it to burn off the alcohol. (Be very careful if this is your first time flambéing, as the flame can be hard to see or may flare up. After about 20 seconds, cover the pan with a plate or lid to extinguish the flame. VERY important: turn off the range hood to avoid a fire hazard.)

Once the alcohol has burned off, pour the brandy or cognac into the skillet with the cream and broth. Add the ground pepper and stir with the wooden spoon. In about 10-15 minutes, the sauce will be ready. It should be somewhat thick.