The Carême classic involves many laborious procedures. This extremely simple contemporary version uses just three ingredients - a basic brown sauce, mushrooms and tomato purée. Skimming the sauce helps make it glossy.
Heat 750 ml brown sauce over a moderate heat until simmering and add 150 g finely chopped mushrooms. Stir until well combined.
Add 1 tbsp tomato purée and stir until evenly blended into the sauce, then continue simmering over a low heat.
Simmer for a total of 15 minutes, skimming often. Strain before using.