Dark Romance Chocolate Blackberry Cake

Name: Dark Romance Chocolate Blackberry Cake
Cook time: 1 h 30 min
Total time: 1 h 30 min
Cuisine: European
Ingredients: 2 cups all-purpose flour; 2 cups sugar; 3/4 cup unsweetened cocoa powder; 2 teaspoons baking powder; 1.5 teaspoons baking soda; 1 teaspoon salt; 1 teaspoon espresso powder; 1 cup milk, buttermilk, almond, or coconut milk; 1/2 cup vegetable oil, or melted coconut oil; 2 large eggs; 2 teaspoons vanilla extract; 1 cup boiling water; 1 cup fresh blackberries, chopped (extra whole blackberries for decoration); 1 cup unsalted butter, softened; 4 cups powdered sugar; 1/2 cup blackberry puree (from fresh or frozen blackberries strained to remove seeds); 1 teaspoon vanilla extract; A pinch of salt; Purple or aubergine food coloring (optional); 1 cup heavy cream; 1 cup dark chocolate, finely chopped; 2 tablespoons light corn syrup or honey (this is the secret to the gloss); 1/2 teaspoon vanilla extract (optional)