Preheat your oven to 170°C/gas mark 3. Line your square tin with foil and grease it, or grease your foil tray.
Put the butter, syrup, muscovado sugar, Guinness, ginger, cinnamon and ground cloves into a pan and melt gently over a low heat.
Take off the heat and whisk in the flour and bicarb. You will need to be patient and whisk thoroughly to get rid of any lumps.
Whisk the sour cream and eggs together in a measuring jug and then beat into the gingerbread mixture, whisking again to get a smooth batter.
Pour this into your lined square tin, or into a barbecue-type foil tray, and bake for about 45 minutes; when it’s ready it will be gleamingly risen at the centre, and coming away from the tin at the sides.
Let the gingerbread cool before cutting into slices or squares.
Yields 24 small squares or 16 generous rectangular slabs.
Recipe courtesy of Nigella.com