Preheat the oven to 350°F (175°C). Grease and flour a cake pan.

In a large bowl, whisk together the all-purpose flour, cocoa powder, baking powder, baking soda, and salt.

In another bowl, beat the granulated sugar and vegetable oil until well combined. Add the eggs one at a time, mixing well after each addition.

Stir in the vanilla extract, buttermilk, and cooled coffee.

Gradually add the dry ingredients to the wet mixture, mixing until just combined.

Fold in the finely ground dried lavender and fresh blueberries.

Pour the batter into the prepared cake pan and bake for 35 minutes or until a toothpick inserted into the center comes out clean.

While the cake is baking, combine the sugar, lemon juice, cornstarch mixture, and fresh blueberries in a saucepan over medium heat. Cook until the blueberries burst and the mixture thickens.

For the chocolate ganache, heat the heavy cream in a saucepan until just boiling. Remove from heat and stir in the dark chocolate chips and dried lavender until smooth.

Once the cake is baked and cooled, drizzle the blueberry mixture on top, followed by the chocolate ganache.

Garnish with edible lavender flowers and chocolate shavings.