Ensure your cream cheese is at room temperature before you begin. This makes it easier to mix and prevents lumps in your dressing.

In a medium bowl, use an electric mixer on medium speed to blend the cream cheese until it is smooth and creamy. Add the sour cream and continue to mix until the two are well incorporated. The sour cream not only adds a slight tanginess but also helps to lighten the density of the cream cheese, making for a more spreadable consistency.

Once your base is smooth, add the granulated sugar and vanilla extract. Mix at medium speed until all the sugar has dissolved and the mixture is smooth. The vanilla adds a layer of subtle sweetness and aroma that enhances the overall flavor of the dressing.

Before proceeding, taste your dressing. Depending on your preference and the sweetness of your grapes, you might want to adjust the amount of sugar or vanilla. If the dressing is too thick, you can add a little more sour cream to thin it out.

For the best results, cover and chill the dressing in the refrigerator for at least 30 minutes before mixing it with the grapes. This not only helps the flavors meld but also makes the dressing easier to spread, ensuring a more even coating on the grapes.