Toast the sourdough bread slices until golden and crisp.
In a medium mixing bowl, vigorously whisk together the liquid egg whites, whole egg, Greek yogurt, nutritional yeast, sea salt, and black pepper until the mixture is frothy and well-combined.
Heat the ghee in a high-quality non-stick skillet over medium-low heat, ensuring the surface is evenly coated.
Pour the egg mixture into the skillet and let it sit undisturbed for about 30 seconds to allow the bottom to set.
Using a silicone spatula, gently push the eggs from the edges toward the center, creating large, soft folds.
Continue to cook slowly, folding occasionally, until the eggs are mostly set but still appear moist and velvety.
Spread the mashed avocado evenly across the toasted sourdough slices.
Mound the fluffy egg whites on top of the avocado and garnish with finely chopped fresh chives before serving.