Preheat oven to 350º F. Lightly spray your donut pans with cooking spray and set aside.
Mix together the dry ingredients: flour, baking powder, baking soda, salt, Truvia or sugar and cocoa powder.
Add in egg, butter, buttermilk and vanilla and mix together. If too thick, add in a little milk until thinned out a bit. (You don't want it too thin, though! More like cake batter thick.)
Spoon into donut pans, about 3/4 of the way full. Bake in preheated oven for 7-9 minutes, or until a toothpick comes out clean.
When donuts have cooled a bit, dump from the donut pan.
Icing: Mix together powdered sugar and cocoa powder. Add in milk one tablespoon at a time until the desired glaze consistency. You don't want it too thick but not too runny.
Dip each donut into the glaze and place on cooling rack. Sprinkle with sprinkles or whatever topping you like.
Enjoy with a glass of Real California Milk!