Preheat oven to 375°F. Butter an 8-inch x 8-inch baking dish and set aside.
Melt butter in a small skillet over medium heat. Stir in Panko and cook until golden brown, about 3 minutes. Transfer to a small bowl, season with salt and pepper and set aside.
In a large bowl, beat cream cheese with a handheld mixer until light and creamy, about 2 minutes. Beat in mayonnaise, sour cream, garlic powder, 1 teaspoon salt and black pepper until smooth. Mix in Parmesan, mozzarella and artichokes. Transfer to prepared dish and smooth top. Sprinkle breadcrumbs over the surface.
Bake for 25-30 minutes until hot and bubbly. Serve hot with baguette slices, crackers or chips.