Heat oven to 350 degrees. Spray a donut pan with non-stick cooking spray.
In a medium bowl mix together the flour, sugar, baking soda, baking powder and salt. In a separate bowl whisk together the half and half, egg, vanilla, butter and Nutella. Pour the Nutella mixture into the bowl with the dry ingredients and mix until the batter just comes together.
Spread batter evenly with a spoon into the donut pan, only fill up each mold halfway. Bake for 10-12 minutes, don’t overcook. Place on a rack to cool before adding the frosting.
While the donuts are cooling, whisk together the powdered sugar, Nutella and half and half until the frosting is creamy. Dip the tops of each donut into the frosting. Before the frosting hardens, add either the crushed hazelnuts or powdered sugar topping. Enjoy!
Recipe by Big City Tiny Kitchen at https://bigcitytinykitchen.com/nutella-donuts/