A few words about this item from chef José Andrés:

Probably the perfect olive, this varietal called Hojiblanca has been grown since ancient times in Cordoba, Spain, because of its hot, dry climate. Collected by farmers in August when the olive is green, they have a distinctive strong, bitter flavor. The olives are cured and then crushed before being packed to make the flesh more tender. Nothing else is added, but I love to marinate them with some fresh peeled garlic or a stalk of tarragon - the crushed olives absorb almost any flavor. I use them in everything: tapas, potato salad or even a good martini - now that is an astonishing cocktail!