I used a 1.5 inch round cutter and got about 40 doughnuts of about 2 inch diameter.
These are best served the same day or next but can be stored in an airtight container for 2 days.
You can fill them before hand but roll in sugar just before serving or else the sugar will get absorbed into the doughnuts in some hours.
You can warm them in the microwave.
To make Nutella more easy to work with , you can warm it up over stovetop or microwave.
You can simply mix together the cinnamon and sugar if using castor sugar - adjust amount of cinnamon according to your tastes. 2 teaspoons might be too strong for some.