Rinse the blackberries. Blend until smooth. Push the puree through a fine strainer to remove the seeds. You’ll need 1 cup for the cake and the rest for the filling.

In a large bowl, beat the butter and sugar until pale and fluffy. This traps air and makes a soft cake crumb.

Add eggs one at a time. Beat well after each. Stir in the blackberry puree and oil until smooth.

In a separate bowl, whisk flour, cocoa powder, baking powder, baking soda, and salt. Add this to the wet mix, alternating with the buttermilk. Stir until just combined. Finish with vanilla extract.

Preheat oven to 350°F (175°C). Grease and line two 8-inch cake pans. Divide the batter between them.

Bake for 25–30 minutes. A toothpick should come out clean. Cool in pans for 10 minutes, then move to a rack.

In a small saucepan, cook blackberries, sugar, and lemon juice over medium heat until the fruit softens.

Mix cornstarch with water. Stir this into the pan. Cook until thickened. Let it cool.

Warm the cream in a small pot until it just starts to bubble. Remove from heat. Pour over chopped chocolate and butter.

Let it sit for 2–3 minutes. Stir until smooth and glossy. Let it cool slightly before using.

Place the first cake layer on a plate. Spread a generous layer of blackberry filling across the top.

Set the second layer on top. Pour ganache over the cake, letting it drip down the sides.

Top the cake with fresh blackberries. Add chocolate shavings and flowers if you like. A dusting of cocoa adds a moody look.