01 - Heat butter in large skillet over medium heat. Add chopped onion and cook 2–3 minutes until translucent, stirring occasionally.
02 - Stir minced garlic into skillet and cook 1 minute until fragrant, taking care not to burn.
03 - Add spinach in batches, stirring until wilted and most moisture has evaporated, approximately 5 minutes.
04 - Pour heavy cream into skillet. Add nutmeg, salt, and pepper. Stir to combine and bring to gentle simmer.
05 - Stir grated Parmesan into sauce until melted and mixture achieves 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 if desired.
08 - Remove from heat and serve immediately. Garnish with additional Parmesan if desired.