Preheat oven to 350 degrees F. Line a 9x9" baking pan with parchment paper and set aside.
In a large bowl combine the muffin mix (just the powder), the softened butter and one egg. Use a wooden spoon, your hands or the paddle attachment on your mixer to combine the ingredients into a soft dough.
Take half of the dough and press it into the bottom of the prepared pan. Spread the chocolate hazelnut spread over the top of the dough, leaving 1/2" of space around the bottom layer. Crumble the remaining dough and sprinkle it over the top of the hazelnut spread, trying to cover it as much as possible.
Bake for 20 to 25 minutes, or until golden brown on top. Let the bars cool completely before removing from the pan and cutting into squares. Enjoy!