01 - Whisk together eggs, milk, salt, pepper, and nutmeg in a bowl until fully blended.
02 - Heat butter or oil in nonstick skillet over medium heat. Cook shallot until translucent, 1-2 minutes.
03 - Add spinach to skillet and stir until wilted, about 1 minute.
04 - Pour egg mixture into skillet, tilting pan to spread evenly over spinach and shallots.
05 - Cook 2-3 minutes until edges set. Gently lift edges with spatula, allowing uncooked egg to flow underneath.
06 - Sprinkle crumbled feta over half of the omelet.
07 - Fold omelet in half when mostly set but still slightly moist on top. Cook 30 seconds, then transfer to plate.
08 - Serve immediately, garnished with extra feta or fresh herbs if desired.