1. Heat your oven to 350 degrees Fahrenheit.
2. In a large bowl mix together flour, baking powder, salt, and baking soda. In another medium bowl, mix together sour cream, milk, and vanilla.
3. In a bowl of an electric mixer or with a hand mixer, cream the butter and sugar until light and fluffy, about five minutes. Beat in the eggs one at a time until combined. Make sure you scrape the sides.
4. Put speed at low and mix in 1/3 of the flour mixture and then 1/3 of the sour cream mixture. Repeat until both mixtures are incorporated. (The batter will be thick.)
5. Dollop 1/4 cup scoops onto your baking sheet, spread apart by two inches. Bake for six minutes, rotate the baking sheets, and bake for six to nine minutes more. The cookies are done when pressed lightly in the center, they spring back. They will only brown on the bottoms.
6. When the cookies are cooling, make the glaze. Start by putting the confectioners’ sugar in a medium bowl and whisking in three tablespoons of boiling water, corn syrup, vanilla, and salt. (BE CAREFUL.) The glaze should be the consistency of hot fudge sauce.
7. Flip each cookie over and spoon glaze over half on the flat side. Place on rack to cool.
8. Once you’re done with the vanilla glaze, turn it into chocolate by whisking in the cocoa and melted chocolate with room temperature water to make it the same consistency. Glaze the other half of the cookie and let set for one to two hours before serving for the glaze to set.