Thickening vegan Avgolemono is a cinch without using eggs! Simply whisk together a couple of tablespoons of cornstarch or arrowroot powder with a small amount of cold vegetable broth until it forms a smooth slurry. Then, gently stir the slurry into your soup while it's simmering, and let it cook for a few minutes until it reaches your desired thickness. Easy, peasy, lemon squeezy!