Preheat your oven to 350°F (175°C) and grease and line four 8-inch round cake pans with parchment paper.

In a large mixing bowl, whisk together all the dry ingredients: all-purpose flour, sugar, unsweetened cocoa powder, baking powder, baking soda, salt, and espresso powder.

Create a well in the center of your dry ingredients and add the wet components: milk, vegetable oil, eggs, and vanilla extract. Blend until smooth and creamy.

Carefully stir in the boiling water and fold in the fresh blackberries.

Divide the batter evenly among the prepared pans and bake for 30-35 minutes until a toothpick comes out clean.

Allow the cakes to cool in the pans for about 10 minutes, then transfer them to wire racks to cool completely.

Beat the unsalted butter in a mixing bowl until fluffy, then gradually add powdered sugar and blackberry puree until smooth.

Heat heavy cream until it simmers, then pour over chopped dark chocolate and stir in corn syrup or honey until smooth.

Assemble the cake by layering frosting between each cooled layer and pour ganache over the top, allowing it to drizzle down.

Garnish with fresh blackberries and serve with whipped cream or vanilla ice cream.