For the volcano cakes: Coat 12 mini bundt pans with cooking spray. (If working with fewer than 12 pans, coat the pans with spray between batches.)
Prepare the chocolate cake batter according to the package directions. Pour the batter into the prepared pans. Bake until a cake tester comes out clean. Remove from the oven and let cool. Using a 1/4 teaspoon measure, scoop small chunks from the center of each cake to create a "crater."
For the chocolate lava: Put the white chocolate chips in a microwave-safe bowl. Heat in the microwave in 15-second increments, stirring after each, until the chocolate has completely melted. Add a few drops of food coloring and stir to combine. Continue adding food coloring until desired color is achieved.
Transfer the cakes to serving plates and pour chocolate lava over each volcano cake. Sprinkle with the rock candy.