01 - Whisk together milk, cream, sugar, cocoa powder, and salt in a medium saucepan. Heat over medium heat, stirring frequently, until mixture is hot and sugar dissolves completely. Do not allow to boil.
02 - Remove saucepan from heat and stir in vanilla extract until fully incorporated.
03 - Pour mixture into Ninja Creami pint container. Allow to cool to room temperature, then cover and freeze for at least 8 hours or overnight until solid.
04 - Process frozen base in Ninja Creami using Ice Cream setting until smooth and creamy.
05 - Create a well in center of processed ice cream. Add marshmallow fluff, caramel sauce, and chocolate fish or pieces.
06 - Reinsert pint and run Mix-In setting to swirl toppings throughout ice cream until evenly distributed.
07 - Serve immediately for soft-serve texture, or freeze 1-2 hours for firmer scoopable consistency.