Preheat the oven to 325℉ and line a 9x9-inch square baking pan with parchment paper. Leave some parchment paper hanging over the sides for easy removal.
Put the butter, golden syrup, brown sugar, Guinness, ginger, cinnamon, and cloves in a saucepan and melt over low heat, approximately 2 minutes.
Take the saucepan off the heat and whisk in the flour and baking soda. Whisk until the batter is smooth.
In a small bowl, whisk together the sour cream and eggs. Pour the sour cream mixture into the batter and mix until smooth.
Transfer the mixture to the lined baking pan and bake for 45 minutes. Allow to cool in the pan for 1 hour before cutting into slices.