Place dark chocolate, cocoa powder, and salt in top of a double boiler over simmering water. Stir frequently, scraping down the sides with a rubber spatula to avoid scorching, until chocolate is melted and smooth, about 5 minutes. Remove from heat.

Mix sugar and milk powder together in a small bowl.

Place 1 3/4 cups milk and cream in a medium saucepan over medium-high heat. Cook, whisking occasionally, until mixture comes to a full rolling boil. Whisk the sugar mixture into the pot. Reduce heat to low and simmer for 2 minutes, whisking to prevent scorching. Remove from heat.

Mix 2 tablespoons milk and tapioca together into a small bowl. Whisk into the hot dairy mixture.

Whisk 1/3 of the dairy mixture into the bowl of melted chocolate. Repeat twice more, whisking well until smooth. Let cool to room temperature, about 15 minutes.

Strain mixture into a bowl and refrigerate for 4 hours, or preferably overnight. Make caramelized almonds and toasted marshmallows before churning the ice cream.

Preheat the oven to 350 degrees F (175 degrees C). Line 2 baking sheets with silicone baking mats.

Toast almonds in a dry skillet over medium heat until fragrant, 3 to 5 minutes. Transfer to a bowl. Combine butter, white sugar, brown sugar, milk, and salt in the skillet. Stir until melted together and smooth. Bring to a boil; cook for 2 minutes. Stir in almonds until coated. Pour onto a baking sheet.

Bake in the preheated oven until bubbling, 7 to 8 minutes. Let cool completely before breaking up into uneven pieces.

While almonds are cooling, spread marshmallows out on the second baking sheet.

Bake in the preheated oven until tops are lightly toasted, about 5 minutes. Let cool.

Churn ice cream according to manufacturer's instructions until it reaches a soft-serve consistency, about 20 minutes. Layer ice cream, almonds, and marshmallows in a freezer-safe container. Freeze until firm enough to scoop, at least 4 hours.