Cooking spray, for coating aluminum foil
1 box chocolate cake mix for two 9-inch rounds (or your favorite flavor)
1/3 cup vegetable oil
1 large egg
5 cups chocolate ice cream, softened
1 1/2 cups cold heavy cream
1 tablespoon sugar
4 ounces semisweet chocolate, broken into large chunks
3/4 cup heavy cream
1/4 cup corn syrup
3 tablespoons unsalted butter
1/8 teaspoon kosher salt
Suggested toppings: chocolate sprinkles, chocolate chips, crushed chocolate wafer cookies, maraschino cherries and chocolate-covered raisins, nuts and pretzels