In a heavy-bottom saucepan, melt the butter over medium heat and sweat the mirepoix, occasionally stirring, until softened - 5 min.
Add garlic clove, bouquet garni, tomato paste and cook until golden brown.
Add tomatoes and cook until soft in low heat - 10 min.
Add red wine and deglaze (optional).
Add the hot veal stock.
Temper the brown roux with a little of the veal stock and add to the rest in the pan, stirring to avoid lumps.
Simmer uncovered, skimming any impurities from the surface of the liquid - écumer.
Reduce the liquid by about one-third or until the sauce covers the back of a spoon.
Pass the sauce through a sieve into a bowl discarding the solids.
The Espagnole sauce is ready to use.