Warm the milk, sugar, cocoa powder, 1 cup of the cream and in a saucepan.
Pour the remaining cream into a large bowl and set a sieve on top
Then in another bowl, whisk the egg yolks.
Pour the warm cream/milk mixture slowly add that to the eggs while whisking the whole time! (If you don't, you will be making scrambled eggs!)
Once mixed, add that back to saucepan.
Stir the mixture constantly over medium heat with a heatproof spatula, scraping the bottom as you stir, until the mixture thickens and coats the spatula.
When it reaches 170° and it begins to coat the back of the spatula, you can then pour it through the strainer into the other bowl with the cream in it.
Add the vanilla.
Chill the mixture thoroughly in the fridge for at least 2 hours or overnight.
When ready make the ice cream, freeze the ice cream according to the manufacturer's instructions.
Before the last few minutes of churning, melt the marshmallow fluff in the microwave until it is easy to pour. It should only take about 20-30 seconds.
Drizzle it into the maker while it churns.
If you want you can also add marshmallows at the end!