Line cupcake pan with cupcake liners. Preheat oven to 350 degrees.

In a large bowl mix together cake mix, prosecco, melted butter and egg whites.

Fill cupcake liners evenly and bake 15-17 minutes or when a toothpick inserted into the middle of a cupcake comes out clean.

While cupcakes bake, make icing.

In separate bowl mix softened butter until light and fluffy. Alternate powdered sugar and prosecco. Starting with powdered sugar. Finish with vanilla. Icing can be stored in the refrigerator until cupcakes cool.

When cupcakes are finished baking, allow them to cool for 10 minutes in the pan. Then move them to a cooling rack. Allow them to cool completely.

Next, use a large frosting tip or a paring knife to remove the center of the cupcake. Make just enough room for one large blackberry.

Finally, Frost and decorate your cupcakes. Ending with another fresh blackberry on top.