This is the traditional sauce, essential accompaniment of any
Argentinean BBQ. Its famous for the fact that there are as many recipes
as there are cooks!
For our mobile gourmet BBQ catering we use the following recipe:

Ingredients:


chopped garlic
parsley
oregano
grounded cumin
basil
olive oil
lemon juice
vinegar
salt
black pepper
hot chillies
sweet paprika

Preferably (as with everything!) use fresh and quality ingredients.
Finely chop the garlic, parsley, oregano, sweet paprika and basil, then mix with oil,
lemon juice, a bit of salt (not much, because the meat and chorizos
should be salted), black pepper and vinegar.
 I also like to ad a bit of grounded cumin, which is not in the traditional recipe, but I think that's what cooking is about. 
Let it marinate for a day (the longer the better).
The proportions of the ingredients is for you to experiment and find your way!

Etymology of the word "Chimichurri"

According to oral tradition, this word derive from the English! When
the English land owners enjoyed the beautifully barbecue prepared by
the gauchos (cattle station workers), they said "give me the curry"
("givmidecurri") which ended up been Chimichurri.

Hola!
 My mum sent this brochure from Buenos Aires, its a promotion for a White goods Shop from around 1965. At the back is this instructions on "how to cook a BBQ".
Enjoy

Señor BBQ
Catering & Entertainment
www.argentineanbbq.com