Preheat oven to 180C (350F). Lightly grease two mini donut pans*.
In a medium bowl, whisk together baking powder, salt nutmeg and flour. Set aside.
In another bowl, whisk together egg, milk and vanilla. Set aside.
In the bowl of a stand mixer, or using a hand mixer, cream together the butter and sugar until light and fluffy.
Add the wet ingredients in two parts (mixture may look curdled), alternating with the dry ingredients. Mix last addition of dry ingredients just until combined; do not overmix.
Spoon the batter into a piping bag or a large ziplock bag with a corner cut off. Pipe batter into the donut pan, filling each donut cavity ½ full.
Bake for 10-12 minutes, or until donuts spring back when lightly touched. Tip the donuts out onto a wire rack.
While the donuts are baking, melt the 113g butter for the coating. In another bowl mix the cinnamon and sugar together until completely combined. Pour the cinnamon-sugar mixture into a large ziploc or paper bag (you're going to shake the donuts in the mixture!).
To coat the donuts, when they're just cool enough to handle, dip each donut quickly in the melted butter, gently shake off excess butter, then put the donut in the cinnamon-sugar bag. Seal the bag and gently shake, turn and invert the bag to completely coat the donut. When coated, open the bag, gently shake off excess and place on a gorgeous serving plate to enjoy!
Store in an airtight container for a day or two, but best eaten within 24 hours.