Preheat your oven to 350?F (175?C). Line a standard 12-cup muffin tin with paper cupcake liners.

In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt until well combined. Set aside.

In a large bowl, whisk together the melted butter and brown sugar until smooth. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract, buttermilk, and mashed blackberries until combined.

Gradually add the dry ingredients to the wet ingredients, mixing gently until just combined. Do not overmix.

Slowly pour in the hot coffee or hot water, stirring until the batter is smooth. The batter will be thin, which is normal.

Divide the batter evenly among the cupcake liners, filling each about ? full.

Bake in the preheated oven for 18-22 minutes, or until a toothpick inserted into the center of a cupcake comes out clean or with just a few moist crumbs.

Remove from the oven and let the cupcakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before frosting.

While the cupcakes are cooling, prepare the blackberry pur?e for the frosting. Blend fresh blackberries in a blender or food processor until smooth, then strain through a fine-mesh sieve to remove the seeds.

In a large bowl, beat the softened butter with an electric mixer until creamy, about 2 minutes. Gradually add the powdered sugar, mixing on low speed until incorporated.

Add the strained blackberry pur?e and vanilla extract, mixing until combined. If needed, add heavy cream one tablespoon at a time until you achieve the desired consistency. Beat on medium-high speed until light and fluffy, about 3-4 minutes.

Once the cupcakes are completely cooled, pipe or spread the blackberry frosting onto each cupcake.

If desired, garnish each cupcake with a fresh blackberry, chocolate shavings, or edible flowers. Serve at room temperature for the best flavor and texture.