Preheat your oven to 350°F. Line a cupcake pan with your favorite paper liners. This makes clean-up way easier.
In a bowl, whisk egg yolk, 3 teaspoons sugar, and cornstarch until the mix is smooth and kinda glossy. This smooth base is key.
Slowly pour in champagne and cold butter, whisking till it’s all combined. You’ll spot the batter start to look velvety.
In another bowl, mix all-purpose flour, baking powder, and salt well. This dry mix is gonna help your cupcakes rise perfectly.
Add the dry ingredients gradually to your wet mix. Stir just enough so everything’s blended—don’t overwork it or they get tough.
Fold in your diced fresh peaches gently. You wanna keep those chunks intact for little juicy bursts.
Grab your lined pan and spoon batter into each liner about ⅔ full. This leaves space for rising and avoids mess.
Bake for 20 to 25 minutes or until you can stick a toothpick in and it comes out clean. Let them cool 5 minutes in the pan, then move them to a wire rack till fully cool before frosting.
Notes
Serve these peach Bellini cupcakes fresh and watch everyone enjoy the festive flavors.