Preheat your oven to 180ºC and line 3 cake pans (6 inches) with parchment paper*. Grease the sides of the pans with butter.
In a glass, pour the milk and add the vinegar. Let it sit while you prepare other elements of the cake.
In a large bowl, beat the butter and sugar together, by a hand beater or a whisk, until light and fluffy.
Add the vanilla to the mixture and combine well.
In a separate bowl, whisk together flour and baking powder
Add the flour alternately with milk to the butter mixture.
Scrape down the side of the bowl, and mix the batter well, just until everything is well incorporated. Do not over-mix.
Pour the batter into the prepared cake tins.
Bake for 20-25 minutes, or until a skewer comes out clean when inserted in the centre.
Cool for 15 minutes before demoulding.
After demoulding, cool completely before icing. I would recommend to cool them in the refrigerator for about 2-3 hours, or overnight, wrapped in cling wrap.
For the chocolate ganache frosting
In a large bowl, finely chop the chocolate.
In a saucepan, heat the whipping cream, just until bubbles start to form
Pour the cream over the chopped chocolate.
Using a spatula, mix them well, until all the chocolate has melted. If you still see lumps of chocolate, melt the mixture over a double boiler, or in the microwave in 30 second intervals.
Cool this mixture completely in the refrigerator, for about 1 hour.
After an hour, whip this mixture, using an electric hand beater, until soft peaks form.
For assembling
Fill the frosting prepared in a piping bag
Place a layer of frosting between each layer and spread it evenly with an offset spatula
Coat the cake with a generous layer of frosting
Decorate the top any way you like!
I glazed my cake with a mirror glaze, the recipe link to which is given below!
Notes
*You can also bake a single layered cake, with no frosting. Just divide the recipe in half, and fill a larger cake tin!