Line two baking sheets with parchment paper and set aside.
In a medium saucepan, heat the sugar, butter, milk and cocoa powder over medium heat. Continue mixing until the butter has melted. Bring to a rolling boil, then allow to boil for around 2 minutes.
Turn the burner to low heat. Mix in the Nutella and vanilla until smooth.
Remove from heat, then mix in the oats.
Using a medium cookie scoop, scoop the mixture onto the prepared baking sheet and allow to cool at room temperature.