In a mortar, working in batches, pound the parsley with the mint and oregano. Work in 2 tablespoons of the olive oil, then transfer to a medium bowl. Pound the garlic with the anchovy and add to the bowl. Gently pound the capers and add to the bowl. Stir in the remaining 1/2 cup plus 2 tablespoons of olive oil and the lemon juice. Gently stir in the feta and serve.
The salsa verde can be refrigerated overnight; serve at room temperature.