Preheat oven to 175C.
In a bowl mix together flour, cocoa powder, baking powder, baking soda, sugar and salt.
Add in melted butter, milk, vinegar and vanilla.
Grease and line a 9" * 13" tray and pour the batter. Spread it evenly.
Bake for 20 - 25 minutes or until a tooth pick inserted comes out clean.
Allow it to cool in the pan.
Remove the cake and crumble it to fine crumbs.
Add ganache and knead to a soft dough.
Place it between two parchment sheets and roll it into a thick rectangle.
Spread the filling on the rectangle.
Starting from the longer side, roll the rectangle to a log making sure that there are no cracks on the surface.
Once the log is ready, wrap it in cling film and refrigerate until firm.
Slice it into 1" slices.
Allow it to come to room temperature before serving.
