Olive Relish

Source: Cato, De agri cultura, 119

Ingredients:

150g black olives and 150g green olives (or 300g of either)
4 tbsp red wine vinegar
plenty of olive oil
2 tsp chopped fresh coriander
2 tsp chopped fresh rue (but see Note 1 below)
4 tsp chopped fresh mint
1 tsp chopped fennel leaf
1/2 tsp ground cumin

Method

Remove stones from olives and chop them finely. Pour 3-4 tbsp of olive oil and vinegar over them. Then finely chop the herbs, add them to the mixture along with the cumin and stir. Put the mixture in a small bowl, stir and flatten it, and add some extra olive oil, until the oil covers the mixture.

This uses plenty of olive oil. A good rule of thumb for every Mediterranean recipe for people who aren't from that region is to pour olive oil until it looks like it's enough, and then pour about twice as much on top of that. Trust me, just keep it pouring.

Original recipe

From this translation:

Recipe for a confection of green, ripe, and mottled olives. Remove the stones from green, ripe, and mottled olives, and season as follows: chop the flesh, and add oil, vinegar, coriander, cummin, fennel, rue, and mint. Cover with oil in an earthen dish, and serve.

Note 1: The original recipe uses rue, which was a lot more widespread in Cato's time but not so much today. so it's not too easy to find, especially fresh. Some people also don't tolerate it too well. You can use any bitter herb instead. Spinach is probably the easiest.

Note 2 Fennel leaves aren't too easy to find outside Mediterranean Europe. Finely-diced fennel root will do.