01 - Preheat oven to 375°F for even baking.
02 - Heat olive oil in a large skillet over medium heat. Add chopped onion and sauté until softened and translucent, about 3 minutes. Add minced garlic and stir constantly for 30 seconds until fragrant, being careful not to brown.
03 - Add washed spinach to the skillet. Season with salt, pepper, and nutmeg. Cook, stirring occasionally, until spinach is completely wilted, about 2 minutes. Remove from heat.
04 - Distribute the spinach mixture evenly among 4 lightly greased ramekins or spread into a single 9-inch baking dish. Create a shallow well in the center of each ramekin (or 4 wells if using one dish).
05 - Carefully crack one egg into each prepared well, keeping the yolk intact.
06 - Drizzle approximately 1 tablespoon of heavy cream over each egg. Sprinkle generously with grated Parmesan, ensuring even coverage.
07 - Place in preheated oven and bake for 12-15 minutes. The whites should be fully set while yolks remain slightly runny. Adjust time by 2-3 minutes for firmer yolks.
08 - Remove from oven and let rest for 2 minutes to allow the dish to set slightly. Serve immediately while warm.