In a saucepan, combine butter, milk, sugar, and cocoa powder and heat over medium heat. Bring to a rolling boil and let boil for one minute. Remove your saucepan from the heat.
Add Nutella and vanilla to hot mixture and stir until combined. Add oats and stir until completely incorporated.
Drop by spoonfuls onto baking sheets lined with wax paper. Let cool (or you can eat them all warm and gooey- that's yummy too!).
Notes
For this recipe, I can usually get at least 24 cookies, if I make them smaller I can get 32 cookies.