In a mixing bowl, mix the sugar, butter, and vanilla.
In a saucepan over medium-low heat, whisk heavy whipping cream, flour, salt and berries.
Continually whisk until the sauce thickens and the berries break down. Approximately 5 minutes.
Pour through a mesh strainer, over the butter mixture and strain, leaving the seeds in the strainer. Discard seeds.
Mix the butter mixture with the berry mixture until fully incorporated.
Place the homemade berry frosting into a piping bag.
Once your chocolate cupcakes are cool, pipe the frosting, starting with the outer edge and working your way around the cupcake until you reach the center.