Preheat your oven to 350°F and lightly grease six wells of a standard muffin tin with a touch of olive oil.
Heat the extra virgin olive oil in a non-stick skillet over medium heat and add the ground turkey, breaking it apart with a spatula until browned and cooked through.
Add the baby spinach to the skillet and stir for 1-2 minutes until the leaves are just wilted, then remove the pan from the heat to cool slightly.
In a medium mixing bowl, whisk together the egg whites, whole egg, sea salt, black pepper, and garlic powder until well combined and slightly frothy.
Distribute the cooked turkey and spinach mixture evenly into the six prepared muffin cups.
Pour the egg mixture over the turkey and spinach in each cup, leaving a little room at the top for the eggs to rise.
Sprinkle the crumbled feta cheese evenly over the top of each muffin cup for a salty, savory finish.
Bake for 20 to 25 minutes, or until the egg cups are firm to the touch and the tops have turned a light golden brown.
Allow the muffin cups to cool in the tin for 5 minutes before using a thin knife to gently release them from the edges.