In a small bowl add the frozen raspberries, one tablespoon of sugar, and 1 teaspoon of cornstarch.
Mix the ingredients together and place in the fridge for 2 hours.
While the raspberries are in the fridge, make the simple syrup with ½ cup of sugar and ½ cup of water. Pour these ingredients into a pot and bring the water to a boil. Mix until the sugar has evaporated.
Pour in a small container and place in the fridge to cool.
Once cooled, add in the vodka to the simple syrup as well as the raspberries. Mix until smooth.
Spoon in the raspberry simple syrup to the bottom of a champagne glass (about ¼ full), add in the sparkling wine, and top with St. Germain.
Cheers!