Preheat oven to 425. Grease a 1 1/2 quart shallow baking dish with 1 teaspoon olive oil.
Heat 2 teaspoons olive oil in a large pot over medium heat. Cook and stir onion and garlic in hot oil until lightly browned, 4 to 7 minutes. Add spinach and simmer until spinach is hot, about 5 minutes. Drain any liquid from the mixture and transfer to a bowl.
Pour milk into pot and return pot to medium heat. Melt cream cheese into the milk; cook and stir together about 3 minutes.
Return spinach mixture to pot with 1/2 cup mozzarella cheese and Cheddar cheese; stir to combine. Season the mixture with Worcestershire sauce, salt, and pepper. Pour the mixture into the prepared baking dish and top with 1/2 cup mozzarella cheese.
Bake in preheated oven until bubbly and golden and golden brown on top, 20 to 25 minutes.