Blanch the green beans in boiling water for 2–3 minutes, or steam until just tender. Rinse under cold water, drain and set aside.
Peel the boiled eggs and separate the yolks from the whites. Put the yolks into a small bowl and mash them with the Greek yoghurt and Dijon mustard until creamy.
Put the cooked pasta into a mixing bowl. Add the egg-yolk dressing and chopped fresh herbs, and toss well to coat the pasta.
Chop the egg whites into small pieces and add them to the pasta.
Cut the green beans into bite-sized pieces and add them to the bowl.
Cut the avocado flesh into small chunks and gently fold it into the salad.
Season with freshly ground black pepper and salt if needed. Toss gently and serve immediately.