Preheat your oven to 350°F (175°C) and grease and flour two 9-inch round cake pans.

In a large mixing bowl, combine the dry ingredients: flour, sugar, cocoa powder, baking powder, baking soda, and salt.

Add the wet ingredients: eggs, buttermilk, vegetable oil, and vanilla extract. Beat on medium speed for about 2 minutes until smooth.

Carefully stir in the boiling water to create a thin batter.

Divide the batter evenly between the prepared pans.

Bake in the preheated oven for 30 to 35 minutes or until a toothpick inserted in the center comes out clean.

Allow the cakes to cool in their pans for 10 minutes, then transfer to wire racks to cool completely.

In a separate bowl, whip the heavy cream with powdered sugar until stiff peaks form.

Gently fold in the pistachio paste to create the pistachio cream.

Once the cakes are completely cool, slice each layer horizontally in half.

Spread the pistachio cream between the cake layers.

Use the remaining pistachio cream to frost the top and sides of the cake.

Drizzle melted chocolate ganache over the top of the frosted cake.

Garnish with crushed pistachios.

Slice your cake, serve, and enjoy every delicious bite.