In a medium bowl, whisk together the whole eggs, liquid egg whites, Greek yogurt, sea salt, and black pepper until completely smooth and slightly frothy.
Toast the sourdough bread until golden brown and crispy; if desired, lightly spread a small portion of the ghee onto the warm toast.
Heat a non-stick skillet over medium-low heat and add the remaining ghee.
Add the fresh baby spinach to the pan and sauté for 1 minute until just wilted, then remove the spinach and set aside.
Pour the egg mixture into the same skillet, keeping the heat low to ensure a creamy, custard-like texture.
Use a silicone spatula to gently push the eggs from the edges toward the center, creating soft, delicate curds.
Just before the eggs are fully set, fold in the wilted spinach and grated parmesan cheese.
Remove the skillet from the heat while the eggs still look slightly wet, as they will continue to cook from residual heat.
Pile the creamy eggs high onto the toasted sourdough slice and garnish with freshly chopped chives.