1. Preheat the oven to 180°C (350°F). Grease a loaf tin* (about 30x12cm) lightly and line with a piece of baking parchment. Set aside.

2. Chop the chocolate finely and add it to a heatproof bowl. Add the cocoa powder and instant espresso powder and mix to combine. Add the hot (almost boiling) water and mix until you get a smooth chocolate sauce. Set aside.

3. Add the oil, butter, and brown sugar (or xylitol), and Baileys to a large bowl and mix until well combined. Add the eggs and mix until light and fluffy. Next, add the sour cream and mix it in. Mix the flour with baking powder, baking soda, and salt. Add to the large bowl and fold in. Take about 5-6 tablespoons of the mix out of the bowl and set aside, then add the chocolate sauce to the large bowl and mix until just combined. Pour about half of the batter into the prepared loaf tin. Spoon the light batter you kept on the side on top of the dark batter and make light swirls with the spoon in the light batter (try to stay away from the sides), then top with the remaining dark batter. Try to cover the light batter completely. Bake for 55-65 minutes or until a wooden skewer inserted into the center comes out clean. Take it out of the oven and let it cool down completely.

4. Chop the chocolate for the topping and add it to a heatproof bowl. Melt the chocolate in the microwave or over a pot with simmering water. Pour over the cake and let harden completely before serving.