Prepare the Cake Batter:
Preheat your oven to 350°F (175°C). In a large bowl, mix the chocolate cake mix, milk, eggs, and oil until well combined.
Bake the Cake:
Pour the batter into a greased 9-inch round cake pan and bake for 25-30 minutes or until a toothpick comes out clean. Let it cool completely.
Layer the Ice Cream:
Once the cake is cooled, slice it horizontally in half. Place one layer back in the pan, spread half of the softened chocolate ice cream on top, and then cover with the second layer of cake.
Freeze:
Cover the cake with plastic wrap and freeze for at least 4 hours or until the ice cream is completely firm.
Top it Off:
Once frozen solid, take the cake out of the freezer and remove it from the pan. Top with chocolate ganache and decorate with chocolate shavings or sprinkles.
Slice and Serve:
Slice into generous pieces and serve immediately. Enjoy the ooey-gooey chocolate goodness!