1. Preheat the oven to 350°F. Generously grease and flour a 6-cavity mini bundt pan.
2. In a small saucepan, heat ½ cup (118ml) of rosé over medium heat until bubbling. Reduce heat to medium-low and simmer until it’s reduced to ¼ cup of liquid. Set aside to cool, refrigerating if necessary.
3. In a large mixing bowl, combine the sugar, vegetable oil, egg, egg yolk, and vanilla extract. Beat on medium speed until the eggs and oil are well incorporated, scrape down the bowl as needed. Next mix in the sour cream and beat until well combined.
4. In a separate bowl, sift the flour together with the baking soda, baking powder, and salt. Add half of the dry ingredients to the mixing bowl with the reduced champagne and mix until the flour starts to combine. Then add the remaining dry ingredients and remaining ½ cup of champagne and beat until all ingredients are well combined. Use a spatula to scrape down the sides of the bowl and stir the batter from the bottom to the top to ensure it’s well mixed.
5. To fill the bundt pan, measure out about ½ cup of batter per cake and pour into each cavity of the pan. Bake at 350°F for 12-15 minutes. Test the cakes for doneness by inserting a toothpick into the center of the cupcake. If the toothpick comes out clean, the cupcakes are done. Allow the cakes to cool for about 10 minutes, then use the flat edge of a knife to help loosen the cakes from the side of the pan. Turn out onto a metal cooling rack and cool completely.

For the glaze

1. In a large saucepan, melt the butter over medium heat. Then stir in the sugar and water and whisk to combine. Reduce the heat to medium-low and bring to a boil. Boil for at least 5 minutes until the mixture has thickened, stir occasionally to prevent it from burning. Remove the syrup from heat and stir in champagne.
2. The glaze will thicken as it cools, but you can pour it over the cakes while it’s still warm. You can either put the cakes back into the bundt pan, or place on a sheet tray lined with parchment paper. Poke several holes in the cakes using a toothpick or fork. Pour the glaze over top. Allow the glaze to absorb into the cakes.