In a large mixing bowl, sift together the cake flour, sugar, baking powder, and salt.
Add the buttermilk mixture to the flour mixture and stir until combined.
Carefully spoon the batter into each doughnut pan well until about 2/3 full.
Bake the donuts in the preheated oven for 7-8 minutes, or until the tops of the doughnuts spring back when lightly touched.
Allow to cool in the pan for a 3-5 minutes before removing the doughnuts onto a rack to finish cooling.
Once cooled, you can begin glazing and decorating the doughnuts as you wish.
For the glaze, microwave all the ingredients together in a microwave safe bowl on 50% power for about 1 minute, stirring in-between, until melted. Add additional water (by the half teaspoon), if needed to thin. Dip one half of each doughnut into the chocolate and allow to dry on a drying rack.