Chop all the chocolate first, then take 100g for the cake.
In a saucepan, heat the butter and chocolate over medium heat until completely melted.
Add the sugar, cocoa powder as well as the Baileys and whisk together until you get a silky and lump-free mixture. Remove from heat and cool for a few minutes.
In a large bowl, whisk together the flour and baking powder.
Add the chocolate mixture and mix until you get an even dough.
Add the eggs and mix again. Now you can pour the dough into a buttered cake tin and bake for 40-45 minutes.
Ganache
In a saucepan, bring the liquid cream and Baileys to a simmer.
Add the remaining chocolate and stir regularly until it has completely molten.
Set the liquid ganache aside at room temperature. Stir every now and then, to avoid clumps, until thick enough to spread over the cake.