Preheat your oven to 375°F (190°C) and gather all your ingredients to streamline the cooking process.

In a 10-inch oven-safe or enamel-coated cast-iron skillet, warm the reserved sun-dried tomato oil over medium heat. Add the minced garlic and tomato paste, stirring continuously for 2 to 3 minutes until the garlic releases its aroma and the tomato paste deepens in color.

Remove the skillet from the heat. Add the cream cheese and sour cream, whisking or stirring until the mixture becomes smooth, creamy, and well combined. Gently fold in the spinach, Parmesan, Italian seasoning, salt, pepper, chopped sun-dried tomatoes, and 1 cup of mozzarella. Stir until every ingredient is evenly distributed and the mixture takes on a rich, cohesive texture.

Spread the dip mixture evenly across the skillet, smoothing the surface with a spatula. Sprinkle the remaining 1/4 cup of mozzarella evenly over the top for a perfectly melty finish.

Place the skillet in the preheated oven and bake for 8 to 10 minutes, or until the cheese is completely melted and the edges begin to bubble. Switch the oven setting to broil and cook for an additional 3 to 5 minutes, just until the top layer turns lightly golden and blistered.

Remove from the oven and allow the dip to rest briefly. Garnish with freshly chopped basil for a burst of color and freshness. Serve warm with crisp crostini toast for dipping—the irresistible combination of creamy cheese and sun-dried tomato richness is guaranteed to impress.