Stir the softened butter until creamy, stir in the eggs and sugar until foamy, then stir in the remaining dough ingredients. Pour the batter into the greased and lightly floured donut tin with a teaspoon and smooth it out with a wet finger. Bake in the preheated oven at 160 ° for about 15 minutes.
For the cream, stir the pudding powder with a little milk until smooth, stir this into the boiling milk and cook a thick pudding while stirring. Remove from the plate and stir in the eggnog, then let cool. Mix the soft butter with icing sugar until creamy and mix with the cold pudding. Chill the cream for about 15 minutes.
Cut through the cooled donuts, fill with the cream and dust with powdered sugar. Put the filled rings in a cool place; they taste best when they have been allowed to sit for a few hours.