In a large bowl, combine the vanilla cake mix, eggs, melted butter, and 1/4 cup of champagne. Stir until a soft dough forms.
Cover the bowl with plastic wrap and refrigerate for at least 30 minutes.
Preheat your oven to 350°F (175°C). Line a large baking sheet with parchment paper.
Use a 1.5-tablespoon cookie scoop to portion the chilled dough into balls. Place them about 2 inches apart on the prepared baking sheet. For thicker cookies, chill the scooped dough on the sheet for another 10 minutes.
Bake for 9 to 11 minutes, or until the edges are set and the centers no longer look wet. Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
To make the frosting, beat the softened butter in a large bowl with an electric mixer on medium speed until creamy, about 1 minute. Gradually add the powdered sugar, salt, 1/4 cup champagne, and optional pomegranate juice.
Beat on low speed until the ingredients are combined, then increase to medium-high and beat for 2 minutes, or until the frosting is light and fluffy.
Once the cookies are completely cool, frost them using an offset spatula or a piping bag. Garnish with sparkling sugar before the frosting sets.