Preheat the oven to 180℃/350℉. Butter a 7-inch round cake pan, dust with cocoa powder, and line the bottom with butter/parchment paper.

Mix milk and vinegar to make buttermilk. Set aside till further use.

In a large bowl, sift together the flour, baking soda, salt, and baking powder.

In a large mixing bowl add the butter and sugar. Beat on medium speed until very well combined, stopping to scrape down the bowl a few times during mixing.

Add oil and vanilla to the bowl and beat till combined.

Add eggs and beat on medium speed till well combined. Stop to scrape down the bowl as needed throughout mixing.

In a small bowl mix hot water with instant coffee to make a coffee concoction.

Add a third of the flour mixture to the wet mixture and mix with a spatula till well combined. Add a third of the buttermilk and a third of the coffee concoction. Mix till combined. Continue alternating between the flour, buttermilk, and coffee concoction until combined. Pour the batter into the prepared cake pan.

Bake for 35 to 40 minutes or until the skewer inserted into the cake comes out with a few crumbs. Let the cake cool completely in the pans. Carefully invert the cakes and remove the parchment paper. (The cakes are very tender and delicate so be gentle.)

Heat the heavy cream in a small saucepan till it boils.

Add chopped chocolate into the cream and mix with a spatula till it combines.

Pour the mixture into a bowl and add butter. Mix till well combined.

Cover the surface of the ganache with a cling wrap and refrigerate for at least 30-45 minutes.

Remove the cling wrap and beat on medium speed till the ganache becomes creamy and volume increases.

Cut the cake horizontally to make 2-3 layers.

Place the first layer on a cake stand or a flat plate. Spread ¼ of ganache. Repeat the process with each layer. On the last layer spread the remaining ganache and spread to cover it.

Top with some chocolate chips. (optional)