Chocolate Peanut Butter Earthquake Cake. 1 box Chocolate Fudge cake mix, plus ingredients needed to prepare (eggs, oil, water) ½ cup butter 8 oz cream cheese, softened ½ cup creamy peanut butter ½ tsp vanilla extract 3½ to 4 cups powdered sugar ½ cup chocolate chips 1 cup miniature chocolate peanut butter cups, halved