In a deep large bowl, mix eggs, milk, sugar and cinnamon. Stir it using a fork and keep aside.
Now coat nutella on one side of 2 toasts and then close both the toasts together by sandwiching the nutella sides in between. Soak the nutella stuffed toast in the egg mix and push it using a knife so it gets coated properly.
Let it sit for 3-5 mins and then flip and let the other side gets coated too same way. Soak the sides as well.
Once ready, cook it on a preheated pan with butter for around 5 minutes on each side until nicely browned but not burnt. Sprinkle some powdered sugar and serve with black coffee. Repeat for the next one in the same way.