Preheat oven to 350. Grease (donut pan) with oil or cooking spray.
Whisk together the sour cream, egg, vanilla, oil, & sugar in a bowl.
Add flour, soda, salt, & nutmeg (optional) & stir together until well combined.
Fill donut pan with batter & bake for 12-16 minutes or until the top is springy to the touch & the sides are turning golden brown. Remove from oven & let cool in pan for 5-10 minutes then transfer to cooling rack.
For the Glaze: In a small bowl, combine powdered sugar & milk together. Glaze should be thin so you can easily dip the donuts to glaze them. You may need to add a little more milk or powered sugar to get the right consistency. (*You can add a tablespoon Grand Marnier for a little something extra*)
Once the donuts have cooled down a bit dip the donuts into the glaze, flipping them over so both sides get covered. Set on a cooling rack to dry. Place a piece of waxed paper or paper towel under the cooling rack for easier clean up from the dripping glaze.