Pre-heat oven to 425 degrees and lightly oil an 8x8 baking dish.
In a large saucepan, add olive oil over medium heat. Once hot, add onion and garlic and cook until lightly brown about 5-8 minutes.
Add milk and cream cheese to saucepan and turn heat to high. Whisk together until cream cheese is completely blended into milk.
Add spinach, Worcestershire sauce, Tabasco, ½ cup mozzarella, salt, and pepper to the saucepan. Stir until mixture is fully combined and cheese is melted.
Pour mixture into prepared baking dish and sprinkle remaining mozzarella cheese on top.
Bake for about 20-25 minutes, until golden brown and bubbly.
Serve spinach dip hot with pretzels, baguettes, breadsticks, crackers, etc.