Put 2 cups of the bone broth in a small jug and stir in the Egg White Protein. Let sit to allow the powder to dissolve.
Put the remaining cup of the broth in a pan with the celery, cauliflower, and peeled cucumber. Bring to the boil. Reduce the heat and simmer for 15 minutes until the veggies are very soft.
Meanwhile, cut the chicken into very small pieces and the mushrooms into small pieces.
Carefully transfer the broth and veggie mixture to a blender. Add the sea salt, Greek yogurt, and lemon juice. Blend on high for one minute.
Stir the broth and Egg White mixture. With the blender running, carefully pour the mixture through the hole in the lid. It will be thick.
Blend on high for at least five minutes to allow the egg white to cook without becoming lumpy.
Meanwhile, add the avocado oil to the pan you used to cook the veggies in and place over medium heat.
Add the chicken and sauté for 10 minutes.
Add the mushrooms, stir, and sauté for another minute. Turn the heat off.
Carefully tap the konjac flour through the hole in the lid of the blender and blend for one minute.
Pour the soup into the pan with the chicken, mushrooms, and juices and stir well.
Add the chopped fresh sage, stir, and serve.