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

In a large bowl, whisk together flour, sugar, cocoa powder, baking powder, and salt.

In a separate bowl, cream together softened butter and egg whites until light and fluffy.

Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined.

Stir in vegetable oil and vanilla extract.

Pour batter into the prepared pan and bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

Let the cake cool in the pan for 10 minutes before inverting it onto a wire rack to cool completely.

While the cake is cooling, prepare the chocolate buttercream frosting.

In a large bowl, cream together softened butter, vanilla extract, and salt until light and fluffy.

Gradually add the powdered sugar and cocoa powder, alternating with the heavy cream, beginning and ending with the powdered sugar. Mix until smooth and creamy.

Once the cake is completely cool, frost it with the chocolate buttercream.

To make the ganache, combine melted dark chocolate and heavy cream in a small bowl and stir until smooth. Pour over the frosted cake and let it set.

Decorate as desired with fresh fruits, edible flowers, or sprinkles.