01 - Whisk together eggs, milk, salt, pepper, and nutmeg in a medium bowl until fully combined.
02 - Melt butter in a nonstick skillet over medium heat. Add shallot and sauté 1 minute until fragrant.
03 - Add spinach to skillet and cook, stirring constantly, for 1-2 minutes until wilted.
04 - Pour egg mixture over spinach in skillet. Let cook undisturbed for 1-2 minutes until edges begin to set.
05 - Gently lift edges with spatula, allowing uncooked egg to flow underneath. Cook 1-2 minutes until almost set.
06 - Sprinkle crumbled feta evenly over one half of the omelet.
07 - Fold omelet in half using spatula. Cook 1 more minute until feta is warmed through.
08 - Slide onto plate and serve immediately.