Take a 9x13-inch baking tray and grease it before lining it with parchment paper.

Preheat the oven to 350 degrees Fahrenheit or 175 degrees Celsius.

In a medium mixing bowl, sift all-purpose flour, cocoa powder, baking soda, baking powder, and salt.

Then, add the granulated sugar into the bowl, and mix it well.

Take another large bowl and add sour cream, eggs, vegetable oil, buttermilk, and vanilla essence

Mix everything until well combined.

Now, add the dry ingredients to the wet ingredients and mix everything well until everything is properly combined.

Add hot water to instant coffee and whisk it into the batter.

Pour the batter into the sheet pan and preheat the oven to 350 degrees Fahrenheit or 175 degrees Celsius.

Now, bake the cake for about 30 to 35 minutes or until a toothpick inserted into the center comes out clean.

Let the cake cool down to room temperature before frosting it.

Put a pan on the stovetop and add heavy cream.

Bring it to a simmer over medium-low heat.

Add cocoa powder, powdered sugar, instant coffee, salt, and vanilla essence before mixing them well.

Now, add butter and semi-sweet dark chocolate, and mix everything continuously until the chocolate is melted.

Remove the mixture from the pan and sift it through a sieve.

Wrap it with plastic wrap and let it cool to room temperature.

Refrigerate the frosting for 30 to 60 minutes, depending on the desired thickness.

Take the frosting out of the refrigerator and beat it at medium speed for 1 to 2 minutes until it turns smooth and creamy.

Now, frost the cake evenly and add chocolate chips on top.

Cut the slices to your desired size and serve them to your guests.