In a large bowl, add all donut hole ingredients and blend with electric mixer until combined, about 2-3 minutes. Lightly grease mini muffin pan with baking spray. Spoon (using a 1Tbsp scoop) into muffin cups and bake in a 350 degree oven for about 13-15 minutes.
Remove from oven and cool about 5-10 minutes in pan. Flip each donut hole onto it's side, as it makes it easier to fill with Nutella. Fill a piping bag with Nutella, and using a tip (I used a size 5 tip), squirt the Nutella into the side of the donut hole, applying enough pressure to see the donut hole expand. Repeat until all donut holes are filled.
Melt butter and place in small bowl. Add sugar to a separate bowl. Drop donut into the butter, roll around. Then drop into sugar, coating generously. Allow to set (about 10 minutes). ENJOY. These are best enjoyed in 24 hours.