This rich, dark cake is the perfect way to celebrate St. Patrick's day. The heady mix of chocolate, Guinness and coffee flour create a deep, smooth sponge which is offset by the sticky sweet marshmallow frosting. It's worth noting that this is a very moist cake due to the amount of liquid ingredients used, so don't make the mistake of thinking it's underdone. When finished, the cake even looks like the famous Irish stout with a dark velvety body and creamy head. Delicious!\nFor One Cake\nIngredients\n\n250ml Guinness\n250g unsalted butter\n75g cocoa powder\n400g caster sugar\n75ml sour cream\n75ml of Strong Coffee\n2½ tsp bicarb. of soda\n275g plain flour\n2 large eggs\nPinch of salt\n\n\n\n\n\n\nMethod\n\nPreheat the oven to gas mark 4\/180°C\/350ºF and butter and line a 21lb loaf tin with parchment paper.\nPour the Guinness into a large wide saucepan with the butter and heat until melted before whisking in the cocoa powder and sugar. Beat together the sour cream, espresso and eggs and add to the pan, then whisk in the flour and bicarb.\nPour the cake batter into the greased and lined tin and bake for 45 minutes to an hour. Leave to cool completely in the tin on a cooling rack, as it is quite a moist cake.\n\n\nFor the Marshmallow Icing\nIngredients\n\n(A cooking thermometer is also required for this part of the recipe)\n4 egg whites\nGenerous 1\/8 tsp cream of tartar\n150g granulated sugar\nPinch of salt\n\nMethod\n\nIn the bowl of a stand mixer, stir together the egg whites, sugar, cream of tartar, and salt. Set the bowl over a saucepan of simmering water, making sure that the bowl has some clearance.\nHeat, stirring attentively and scraping down the sides of the bowl periodically with a silicone spatula, until the mixture reaches 80°C\/ 175°F on a cooking thermometer (this should be about 8 minutes).\nTransfer the whites to the stand mixer with the wire whisk attached. Beat, starting slow and increasing the speed steadily, until the mixer is on full. Whip until the stiff, glossy peaks form.\nPlace the frosting on top of the cooled cakes and Use a blow torch or place under the grill to caramelise.\n\nEnjoy!