Heat olive oil in a large cast iron skillet over medium heat. Add onion and cook, stirring frequently, until translucent, about 2-3 minutes.

Stir in garlic until fragrant, about 1 minute.

Stir in wine, scraping any browned bits from the bottom of the skillet.

Stir in spinach, artichokes and red pepper flakes until warm and excess liquid has reduced, about 4 minutes.

Stir in cream cheese and sour cream until melted and heated through, about 5 minutes. Remove from heat.

Stir in Parmesan; season with salt and pepper, to taste. Sprinkle with mozzarella.

Preheat oven to broil on high. Arrange an oven rack 6-inches from the broiler.

Place skillet into oven and broil until golden brown and bubbly, about 3-5 minutes.

Serve immediately.