Instructions:
- Preheat oven to 375°F (190°C). Thaw the spinach completely, then use your hands or a clean towel to squeeze out every last drop of moisture. Set aside.
- Melt the butter in a large skillet over medium heat. Add the minced onion and sauté until softened and translucent (about 4–5 minutes). Add the minced garlic and cook for one minute until fragrant.
- Remove the skillet from the heat. Add the squeezed spinach to the onion mixture and stir well to combine.
- In a separate large bowl, combine the softened cream cheese, mayonnaise, and sour cream until smooth. Whisk in the Worcestershire sauce, salt, pepper, and nutmeg.
- Fold in 3/4 cup of the Parmesan cheese, the mozzarella, and the fresh parsley into the cream mixture. Then, gently fold in the spinach mixture until just combined.
- Spoon the dip mixture evenly into a greased 9-inch pie dish or 1.5-quart baking dish. Sprinkle the remaining 1/4 cup of Parmesan cheese evenly over the top.
- Bake for 20–25 minutes, or until the dip is hot all the way through and the top is golden brown and bubbling around the edges.
- Let the dip rest for 5 minutes before serving warm with sturdy crackers, pita chips, or crudités.