Bring some water to a boil and cook the pearl couscous according to the instructions (about 9 minutes).
Meanwhile, put half of the watercress, half of the parsley, half of the cilantro and half of the dill in a blender and add some high quality olive oil, half a clove of garlic, some lime juice, the hazelnuts and half of the za'atar to it. Blend to make a herb salsa. Season to taste with pepper and salt.
Now take half of the salsa out of the blender, put it in a small bowl and set it aside.
Add 2 tbsp of hummus and half an avocado to the salsa that's still in the blender and blend again to make a smooth mass. You can add some more lime juice, pepper and/or salt if you wish.