Espagnole Sauce is a rich, beefy sauce with a complex flavor profile. Generally used as a base for other sauces, this recipe is simple to prepare and has many uses in cooking.
In a large saucepan, melt the butter over medium heat. Add the mirepoix (carrot, onion, and celery) and cook until golden, about 8 minutes. Stir occasionally.
Add the flour and cook the roux over medium-low heat, stirring constantly. Cook until brown, about 7-10 minutes.
Pour the hot beef stock, whisking constantly to prevent lumps, in a steady stream. Stir in the tomato paste, bay leaf, and peppercorns. Bring the mixture to a boil, stirring frequently.
Reduce the heat to low and simmer for 30-40 minutes, uncovered, until the sauce has reduced. Stir occasionally and skim the fat off of the top surface.
Run the sauce through a fine-mesh strainer and discard the solids.
Notes
STORAGE - Store cooled sauce in an airtight container in the refrigerator for up to 3 days.
FREEZE - While you certainly can freeze this sauce, I would advise against it. If desired, transfer the cooled sauce to an airtight container and freeze for up to 3 months.