Preheat the oven to 180°C and greasing a round baking dish.
In a bowl, combine milk and vinegar, stir, and set aside for 5 minutes to curdle — this forms your buttermilk.
Add sugar and oil to the above mixture and whisk together until well combined.
Sift in all-purpose flour, cocoa powder, baking powder, and baking soda into the wet mixture. Whisk gently until the batter is smooth and lump-free. Be careful not to overmix — you want a soft and airy sponge.
Pour the batter into the prepared baking dish and bake in the preheated oven for 25–30 minutes, or until a skewer inserted in the center comes out clean.
While the cake is still baking, make the hot chocolate mixture. In a saucepan over medium heat, combine milk, coffee powder, sugar,cocoa powder and dark chocolate. Whisk continuously until the mixture starts to simmer. Stir until completely melted and smooth.
Using the back of a wooden spoon or a skewer, poke several holes all over the warm cake — this will allow the hot chocolate to seep through. Pour the hot chocolate mixture evenly over the warm cake, letting it soak in fully.
In another saucepan, heat fresh cream until it just begins to simmer. Pour it over chopped dark chocolate in a bowl and let it sit for a minute. Then whisk until smooth and glossy. Allow the ganache to cool slightly so it thickens a bit before spreading.
Once the cake has absorbed all the hot chocolate and is slightly cooled, spread the chocolate ganache evenly over the top. Smooth it out with an offset spatula for a sleek finish. Refrigerate for at least 1 hour before serving so everything sets beautifully.
Recipe by Bake with Shivesh at https://bakewithshivesh.com/hot-chocolate-poke-cake/