Espagnole Sauce (Escoffier)

Dissolve the cold roux in a bowl by stirring in some of the cold brown stock.

Heat the rest of the stock in a deep, thick saucepan over a medium-high flame and bring to a boil. Lower the heat.

Temper the roux by ladeling some of the stock into the roux while whisking vigorously.

Stirring constantly, slowly pour the tempered roux into the simmering stock.

Dissolve the tomato paste with some of the stock and stir it into the sauce. Add the mirepoix and the bouquet garni.

Simmer slowly, partially covered for 2 or 3 hours. From time to time skim off any scum.

Add more stock if the sauce thickens too much. You should end up with a sauce that coats a spoon lightly.

Adjust the seasoning to taste. Strain and degrease thoroughly.

Refrigerate or freeze if not using immediately.