01 - Heat butter in large skillet over medium heat. Add onion and sauté 2-3 minutes until translucent.
02 - Stir in garlic and cook 1 minute until fragrant.
03 - Add spinach in batches, stirring until wilted and moisture evaporates, about 5 minutes.
04 - Pour in heavy cream, add nutmeg, salt, and pepper. Stir to combine and bring to gentle simmer.
05 - Stir in Parmesan until melted and sauce reaches creamy consistency.
06 - Make four wells in spinach mixture using spoon. Crack egg into each well.
07 - Cover skillet and cook 6-8 minutes until whites set and yolks remain slightly runny. Adjust time for firmer yolks.
08 - Remove from heat and serve immediately, garnished with extra Parmesan if desired.