Chocolate Blackberry Cream Sponge Cake

Ingredients

• Cake:
• 1/4 cup all-purpose flour
• 1/4 cup cocoa powder
• 1/8 teaspoon salt
• 6 ounces bitter or semi-sweet chocolate, chopped
• 2 tablespoons unsalted butter
• 2 tablespoons water
• 6 eggs, separated, at room temperature
• 1/3 cup sugar or Swerve sweetener
• 1 teaspoon vanilla extract
• 1/8 teaspoon cream of tartar
• Filling:
• 3/4 cup blackberry jam
• 3 tablespoons Celia's Blackberry Ginger Balsamic Vinegar
• 1 cup fresh blackberries, plus more for garnish
• 1 cup whipped cream
• Chocolate Ganache:
• 9 ounces bittersweet chocolate, chopped
• 1 cup heavy cream
• 1 tablespoon dark rum (optional)