01 - Heat butter in a large skillet over medium heat. Add chopped onion and sauté 2–3 minutes until translucent.
02 - Stir in minced garlic and cook 1 minute until fragrant, being careful not to burn.
03 - Add spinach in batches, stirring until wilted and most moisture has evaporated, about 5 minutes.
04 - Pour in heavy cream and sprinkle nutmeg, salt, and pepper. Stir to combine and bring to gentle simmer.
05 - Stir in Parmesan cheese until fully melted and sauce reaches creamy consistency.
06 - Using spoon, create four wells in spinach mixture. Crack one egg into each well.
07 - Cover skillet and cook 6–8 minutes until whites are set and yolks remain slightly runny. Extend cooking time for firmer yolks.
08 - Remove from heat immediately and serve, garnishing with extra Parmesan if desired.