2 (7-ounce) containers plain Greek yogurt, such as Fage
½ cup freshly squeezed lemon juice
4 tablespoons chopped fresh dill
2 tablespoons chopped fresh mint
4 tablespoons minced fresh chives, plus extra for serving
1 teaspoon kosher salt
½ pound feta cheese, diced
Cut the avocados in half and remove the pits. Scoop out the flesh and coarsely chop it, discarding the skins.
Combine all ingredients except the feta in the bowl of a food processor (or powerful blender such as Vitamix) and pulse until combined. Add the feta and 2 tablespoons water and process until completely smooth. If the dip seems too thick (this will depend on the size of your avocados) add an additional tablespoon or two of water and pulse again until smooth.
Serve immediately with crudités or crackers, or refrigerate in a sealed container with a piece of plastic wrap pressed against of the surface of the dip to prevent browning, for up to 24 hours.