Preheat oven to 350 degrees F (175 degrees C). Line a baking sheet with parchment paper.
Combine cake mix, vegetable oil, and egg in a large bowl until well blended; fold in chocolate chips. Spread mixture onto the prepared baking sheet using your fingers, forming into a 9-inch round about 1/4-inch thick. Top with salt.
Bake in the preheated oven until cookie crust is set, 14 to 16 minutes. Remove from oven and knock bottom of baking sheet firmly on the counter to flatten any extra air from cookie crust. Cool crust on the baking sheet, at least 30 minutes. Transfer to a large plate or platter.
Soften ice cream at room temperature for 20 minutes; transfer to a bowl and beat with an electric mixer until the consistency of soft serve.
Spread beaten ice cream over cooled cookie crust with an offset spatula or knife. Transfer to the freezer until firm, about 30 minutes.
Slice ice cream "pizza" into 6 to 8 slices and top each slice with walnuts and hot fudge.
Try a variety of toppings. At least one topping and one sauce, but the sky's the limit! You can do whatever sounds delicious! Hot fudge and M&M's® make an easy winner. Some other great combos: Hot fudge and spanish peanuts; salted caramel and crushed Oreos®; raspberry puree, chopped chocolate, and toasted almonds, just to name a few! Have fun and be creative!
Or better yet, make a little buffet of options and let everyone top their very own ice cream pizza slices.
Save the other 1/2 of the box of cake mix for your next ice cream pizza party OR double the recipe and bake two now!
Per Serving: 468 calories;28.1 g fat;
50.7 g carbohydrates;
7.2 g protein;
58 mg cholesterol;
337 mg sodium.