I'm not sure what is it with the Nutella, that makes it so versatile when it comes to cooking. Maybe because its a chocolate with sugar and fat (lots of both) already incorporated, so gives us the illusion that we are not using many ingredients.
Anyway, to the muffins.
Mix everything until well incorporated and bake at a pre heated 175º for around 15 minutes or until a skewer comes out dry.
That's it. so simple
(Obviously I'm omiting the, pre heat oven, prepare the cupcake tin bla bla bla you know that)