Preheat your oven to 350°F (175°C) and grease three 9-inch round cake pans, then line the bottoms with parchment paper for easy removal.

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

In another bowl, beat the large eggs and granulated sugar together until fluffy, about 3-5 minutes. Add in the buttermilk, oil, and vanilla extract; mix well.

Gradually add the dry ingredients to the wet mixture, stirring gently until a smooth batter forms. Add the hot water slowly, ensuring it is fully incorporated.

Divide the batter evenly among the prepared cake pans. Bake for about 30 minutes, or until a toothpick inserted into the center comes out clean.

While the cakes cool, blend the blueberries with sugar until smooth, then strain to remove seeds.

Bloom the gelatin in cold water, then dissolve it gently before mixing into the blueberry puree.

Whip the heavy whipping cream until stiff peaks form, then fold gently into the blueberry mixture.

In a separate bowl, whip room temperature cream cheese and unsalted butter together until smooth. Gradually add confectioners' sugar and a splash of vanilla extract, mixing until light and fluffy.

In a small saucepan, combine blueberry juice, sugar, and cornstarch over medium heat. Stir continuously until thickened, about 5-7 minutes.

Once the chocolate cakes have cooled, place one layer on a serving plate and spread a generous layer of blueberry mousse on top. Repeat with the second layer and finish with the third.

Using a spatula, apply a thick layer of cream cheese frosting over the top and sides of the layered cake.

Drizzle the prepared blueberry syrup over the top of the frosted cake, and serve.