Preheat your oven to 180°C (350°F) and grease ramekins or a baking dish.
In a saucepan over low heat, pour the Guinness and warm gently, then add the dark chocolate and butter, stirring until melted and smooth.
Remove from heat and stir in the brown sugar until dissolved.
In a separate bowl, whisk the eggs and vanilla extract, then gradually add the chocolate mixture, mixing until well combined.
Fold in the sifted flour and cocoa powder until you have a smooth batter.
Pour the batter into the prepared ramekins or baking dish.
Bake for 25-30 minutes, or until the puddings are firm to the touch but still soft and gooey inside.
Allow to cool slightly before serving. Enjoy with a scoop of vanilla ice cream or a dollop of whipped cream.