Buttermilk Cream Filling

Beat 1/3 cup cream with an electric mixer until soft peaks form; set aside.

Sprinkle gelatin over 1/4 cup buttermilk in a medium bowl; let stand 5 minutes.

Bring remaining 1/3 cup cream and the sugar to a simmer in a small saucepan over medium heat. Cook, stirring, until sugar has dissolved. Pour into gelatin mixture; stir until gelatin has dissolved. Stir in remaining cup buttermilk and the salt. Pour through a cheesecloth-lined sieve into a medium bowl.

Using a whisk, fold in whipped cream. Refrigerate mixture 30 minutes.