Late to the conversation, but wanted to add a comment. I made this cocktail following the guidance and enjoyed the drink, but decided to experiment a bit, coming up with might be alternatives to consider. First, i replaced the Sauvignon Blanc with Génépy, reducing it by a 1/4 ounce. Next was lowering the simple by 1/4 ounce with the addition of 1/4 ounce of fresh lemon juice. Really loved the solid base cocktail that allowed my experimentation.
Are you using a Cocktail Kingdom Coco Fine Strainer? If not, it may be worth investing in one, as it is better for this than most other fine strainers.
Nice cocktail. The wine provides a slight grape aftertaste. Nicely dry. This is a cocktail which will be greatly impacted by the quality and sweetness of the blueberries and the quality of the wine. Would recommend only making this when blueberries are in season and not being shipped from far way.