In a large measuring cup (easier to pour the cake batter in the paper casings later on) or mixing bowl add the plain flour, baking powder, caster sugar, cocoa powder and a pinch of salt.

Whisk gently until the cocoa powder is fully folded into the flour. Then pour in the Guinness beer.

Stir well until you get a silky and runny batter. Now add the egg.

Stir well again. Then pour in the cooled melted butter.

Stir well. Add the sour cream.

Give the chocolate cake batter one last firm stir. Line a cupcake baking tin with paper casings and fill them with the chocolate batter.

Bake the cupcakes in a preheated oven at 180°C for 25 to 30 minutes until the middle has set. If it is still runny on the inside, bake the cupcakes for another 5 minutes. They should rise nicely. Then remove the cupcakes from the oven and let them cool down.

You can make the cocoa frosting. Blend 1 cup (220 g) of unsalted butter, 1 tbsp of cocoa powder, 2 tbsp of icing sugar and 1 tbsp of sour cream. You should end up with a creamy brown frosting. Transfer it to a piping bag and decorate the cupcakes when they are fully cooled.