3 tablespoons butter
2 tablespoons shallots, peeled, chopped
1/2 cup brandy
1 tablespoon sherry vinegar
2 cups beef demiglace or stock
2 tablespoons green peppercorns
Salt, to taste
In a stockpot over medium heat, melt 1 tablespoon butter. Add 2 shallots and stir often until limp but not brown, 2 to 3 minutes. Add brandy and sherry vinegar. Increase heat to medium-high and boil, stirring often, until liquid is almost evaporated, 5 to 6 minutes. Add beef demiglace or stock. Reduce heat and simmer, stirring occasionally and skimming off any residue that comes to the surface, for 10 minutes. Stir in green peppercorns and salt to taste. Just before serving, over low heat, whisk in 2 more tablespoons butter. Pour into a gravy boat.
