Preheat oven to 350°. In a small bowl, mix sour cream, ricotta cheese, 3/4 cup mozzarella cheese, pepperoni and soup mix until blended. Spread into a greased 9-in. pie plate. Sprinkle with remaining mozzarella cheese.
Bake, uncovered, until bubbly, 35-40 minutes. Serve with baguette slices.