Bring a medium pot of water to a boil. Add the cauliflower and let cook until fork-tender, about 8 minutes. Drain thoroughly and transfer to a food processor. Add the Greek yogurt, butter, garlic, dill, and parsley and process until creamy. Season with salt and pepper to taste, add the Parmesan, and process until just combined.
Transfer to a bowl and garnish with more dill and parsley. Serve hot.