Preheat the oven to 250 degrees and line 2 baking sheets with parchment paper and set aside. In a large bowl or stand mixer fitted with the whisk attachment, beat the egg whites on high speed until soft peaks form. Slowly stream in 3/4 cup sugar and the salt and vanilla. Beat for another 5-6 minutes until hard peaks form and the meringue is very white and glossy. Fold in the Blackberry Patch Syrup to create a swirl. Spoon the puree onto the prepared baking sheets and bake for 40-50 minutes or until the meringues are dry and easily peel away from the parchment. Let cool and store in an airtight container.