Preheat oven to 350°F.

In the bowl of a stand mixer fitted with the paddle attachment, cream together butter and sugar until light and fluffy. Add eggs one at a time beating well after each addition. Add vanilla and mix. Whisk together flour, baking soda, baking powder, salt and ground ginger; set aside. In a small bowl, whisk together 1/2 cup ginger ale and 1/2 cup sour cream (mixture will fizz and bubble a little). Add flour and champagne mixture alternately, beginning and ending with flour. Batter will be thick.

Fill cupcake papers with 1/4 cup level measures of batter. Bake for 17-22 minutes. Set aside.

Place the 1 cup of ginger ale in a small saucepan. Simmer over medium-high heat until reduced to 1/2 cup. Reduce heat to low. In a small cup, whisk together cornstarch and water until no lumps remain. Add mixture to 1/2 cup ginger ale reduction. Whisk constantly as you heat. Mixture will thicken and have a soft gel appearance. Remove from heat and whisk in ground ginger. Transfer mixture to a bowl and allow to cool completely.

In the bowl of a stand mixer fitted with the whisk attachment, cream softened butter and cooled ginger ale mixture together until smooth. Stir in confectioners’ sugar 1 cup at a time on low speed until thickened to piping consistency. You may not have to use all the confectioners’ sugar. Conversely, If the ginger ale gel mixture is added while still slightly hot or if it was not cooked enough, you may need to add more confectioners’ sugar.

Transfer frosting to a piping bag fitted with a large star tip and pipe onto cooled cupcakes. Decorate with white nonpareils.