Preheat your oven to 350°F (175°C). Grease and line two 8-inch or 9-inch cake pans with parchment paper.

In one bowl, mix the dry ingredients: flour, sugar, cocoa powder, baking powder, baking soda, and salt.

In another bowl, whisk the wet ingredients: eggs, vegetable oil, buttermilk, and vanilla extract.

Gradually combine the wet and dry ingredients, then stir in the hot water until smooth.

Divide the batter evenly into the prepared pans. Bake for 30-35 minutes or until a toothpick inserted in the center comes out clean.

Let the cakes cool completely.

In a saucepan, combine the blackberries and sugar over medium heat until juicy.

In a separate bowl, mix the cornstarch with water to create a slurry.

Add this mixture to the saucepan along with the lemon juice, stirring until thickened.

Remove from heat and let it cool fully.

In a mixing bowl, beat the heavy cream, powdered sugar, and vanilla extract until stiff peaks form.

Once the cakes are cool, place one layer on a serving plate.

Spread the blackberry filling over the first cake layer, then add the second layer on top.

Frost the top and sides with the whipped cream.

Decorate with fresh blackberries, dark chocolate shavings, and edible flowers for a beautiful final touch.

For the best results, chill the assembled cake in the refrigerator for at least 1 hour before slicing and serving.