Step 1: Prepare the Spinach

1. Heat 1 tbsp of olive oil in a skillet over medium heat.
2. Add the chopped spinach and sauté for 3-4 minutes until wilted.
3. Remove from heat and let it cool. Squeeze out any excess moisture using a clean kitchen towel or paper towels.

Step 2: Mix the Ingredients

1. In a large mixing bowl, combine the softened cream cheese, sour cream, and mayonnaise. Mix until smooth.
2. Add the minced garlic, chopped onion, salt, black pepper, and red pepper flakes (if using). Stir well.
3. Fold in the cooked spinach, shredded mozzarella, and grated Parmesan cheese. Mix until evenly combined.

Step 3: Transfer to a Baking Dish

1. Preheat your oven to 375°F (190°C).
2. Transfer the spinach mixture to a greased 8×8 inch baking dish. Spread it evenly using a spatula.

Step 4: Bake the Dip

1. Place the baking dish in the preheated oven and bake for 20-25 minutes, or until the top is golden and bubbly.
2. For an extra cheesy crust, broil for 1-2 minutes at the end (keep an eye on it to avoid burning).

Step 5: Serve and Enjoy

1. Remove the dip from the oven and let it cool for 5 minutes.
2. Serve warm with tortilla chips, bread slices, or fresh veggies.