Sauce Espagnole — Brown Roux Mother Sauce

Ingredients

• For the dark roux
• 125 g unsalted butter
• 150 g plain flour, alternatively pre-toasted in a dry oven at 180 °C for 20 minutes
• For the sauce
• 3 litres fond brun (brown stock), hot; beef or veal
• For the mirepoix
• 150 g onion, medium dice
• 100 g carrot, medium dice
• 75 g celery, medium dice
• 30 g unsalted butter, for browning the mirepoix
• For the sauce
• 60 g tomato paste, or blanched, seeded tomato in equivalent quantity
• 1 bouquet garni, bay, thyme, parsley stems
• 1 tsp black peppercorns, whole

Method

1. 1
   If pre-toasting the flour, spread it on a tray and place in a dry oven at 180 °C for 20 minutes, stirring once, until it colours to a pale tan. Remove and cool. This step reduces the stovetop roux time and deepens the nutty character. The flour should smell of warm biscuit, not raw starch.
2. 2
   Melt 125 g butter in a heavy saucepan over moderate heat. Add the flour and stir without pause for 15–20 minutes (or 10–12 minutes if the flour was pre-toasted) until the roux reaches a deep nut-brown — the colour of dark hazelnuts — and carries a pronounced toasted aroma with no raw-flour scent. This is where the dish lives or dies: under-cooked roux will produce a floury, pale, characterless sauce that no amount of simmering will rescue.
3. 3
   Remove the roux from direct heat for 30 seconds, then add the hot fond brun in a slow, steady stream, whisking constantly. Adding cold stock to a hot roux causes lumps and violent splatter; the stock must be hot and the addition gradual. Continue whisking until the liquid is fully incorporated and the sauce is smooth, then return to a gentle simmer.
4. 4
   In a separate pan, brown the diced onion, carrot, and celery in 30 g butter over medium-high heat until the vegetables are deep golden and their edges begin to caramelise. Add the tomato paste and cook a further 2 minutes until it darkens slightly and loses its raw sharpness. Add the browned mirepoix, tomato, bouquet garni, and peppercorns to the simmering sauce. The sauce should smell of roasted vegetables and sweet tomato, not of raw onion.
5. 5
   Simmer uncovered on the lowest possible heat for 4–6 hours, skimming every 20 minutes as fat and grey impurities rise to the surface. Do not reduce below 3 hours: before that point the flour taste persists and the tomato retains its acidity. At the correct stage the sauce tastes of roasted meat and vegetables with no trace of flour, the tomato flavour has mellowed from sharp to sweet, and the colour is a deep mahogany. If a skin forms, lay a cartouche directly on the surface.
6. 6
   Pass the sauce first through a fine chinois, pressing the solids lightly, then through a double layer of muslin without pressing — allow it to drain under its own weight. The strained espagnole should be clear, deep brown, and free of any particulate matter. It is now ready to serve as the base for demi-glace or any brown derivative sauce in the classical canon.