Guinness Black Magic Cake


Woohoo! Only two more days until St. Patrick’s Day and my oh my do I have a phenomenal sweet and boozy recipe for you today…Guinness Black Magic Cake! And magic it certainly is! The rich, dark Guinness cake layers are unbelievable moist and chocolatey and blanketed with an enchantingly delicious Ermine Buttercream frosting which is drizzled with a Salted Whiskey Caramel Sauce. I’m telling you, this cake will leave you spellbound to say the least!


The most surprising thing about this cake for me was that Ermine Frosting. Ermine frosting is an old-fashioned recipe for buttercream. It is also known as Boiled Milk Frosting, Flour Buttercream or Butter Roux frosting. Apparently it was the original frosting for the Red Velvet Cake before Cream Cheese frosting became all the rage. And don’t get me wrong, cream cheese frosting is tasty, but in my humble opinion it can not hold a candle to Ermine Frosting. It was ahhhhh-mazing. So velvety and silky smooth, very light, fluffy and sweet but not toothachingly so. My favorite frosting is Swiss Meringue Buttercream, but Ermine frosting in a very close second. I can’t believe I had no idea it existed before making this cake. Now that I’m “in the know”, I’m sure it will be making appearances here frequently!


This cake was pretty easy to make all in all. The most difficult step for me was the Caramel Sauce. Yup, Caramel sauce and I have a very tempestuous relationship to put it mildly. I tried to make it as Super Golden Bakes indicated in her blog, however I must admit, I failed in my first attempt. So I went back and made a slight adaptation to my Perfect Salted Caramel Sauce, by adding some Irish whiskey and achieved perfection on my first attempt. That is the caramel recipe that works for me, so that is the one I’ve included here.


So go ahead and cast a spell over your St. Patrick’s Day crowd this year with this alluring Guinness Black Magic Cake. I promise you, folks will be completely entranced!


Guinness Black Magic Cake

  • Servings: 8 - 10
  • Difficulty: moderate - mostly because of that tricky Salted Whiskey Caramel Sauce
  • Print

recipe slightly adapted from: Super Golden Bakes


For the cake: (This recipe will make 2 – 9″ cake layers or 3 – 8″ cake layers)

  • 200 g (7 oz) plain flour
  • 350 g  (12 oz ) caster sugar
  • 75 g (3 oz )cocoa powder
  • 2 tsp baking soda
  • 1 tsp baking powder
  • 1 tsp salt
  • 2 large eggs
  • 225 ml  (8 oz) Guinness
  • 225 ml (8 oz) buttermilk or milk soured with 1 tsp lemon juice
  • 100 ml (4 fl oz) coconut oil (can substitute vegetable oil)
  • 1 tsp vanilla extract
  • 1 recipe of Ermine Frosting (to follow)
  • 1 recipe of Salted Whiskey Caramel (to follow)

Preheat the oven to 180°C (350°F). Prepare 3x20cm (8″) pans or 2x23cm (9″) pans – grease and line the bottoms and sides with parchment paper.

Sift the flour, sugar, cocoa powder, soda, baking powder and salt together into a large bowl.

Put the eggs, Guinness, buttermilk, oil and vanilla extract into the bowl of your stand mixer and whisk together on low speed until combined.

Gradually add the dry ingredients and beat for a couple of minutes, scraping the bottom and sides of the bowl. The batter will be fairly thin.

Pour into the cake tins filling only halfway. Bake the 20cm cake layers for about 20-25 minutes (the 23cm cakes take 30-35 minutes) or until the top of the cake is firm and a skewer inserted in the centre comes out clean. Cool on a wire rack.

Pipe or spread the frosting over the layers drizzling caramel over each layer before sandwiching together. Pipe frosting over the top layer and drizzle with caramel. Serve at room temperature (the frosting will harden in the fridge).

Ermine Frosting


  • 200 g  (7 0z) unsalted butter
  • 200 g  (7 oz) caster sugar
  • 235 ml  (1 cup) milk
  • 5 Tablespoons plain flour
  • pinch salt
  • seeds from 1 vanilla pod

Put the milk and flour in a small saucepan and whisk over medium-low heat until the mixture thickens and the whisk leaves a trail. Transfer to a bowl and cover with cling film, pressing it on the surface to prevent a skin forming. Cool completely before using (speed up the process by putting the bowl in the fridge or freezer).

Whisk the butter and sugar together for about minutes, stopping the mixer and scraping the sides and bottom of the bowl as you go. Make sure that the sugar has completely melted before proceeding. Unmelted sugar is what leads to a grainy buttercream, and no one likes that! Once the butter/sugar mixture is smooth and fluffy, then add the vanilla and salt.

Start adding the milk roux, one tablespoon at a time, until the frosting is completely smooth and has the consistency of whipped cream.

Salted Whiskey Caramel


  • 1 cup granulated sugar
  • 1/2 cup heavy cream
  • 6 tablespoons unsalted butter, cut into pieces
  • 2 Tablespoons Irish whiskey
  • 1/2 tablespoon fleur de sel

Add the sugar in an even layer over the bottom of a heavy saucepan, with a capacity of at least 2 or 3 quarts. Heat the sugar over medium-high heat, whisking it as it begins to melt. You’ll see that the sugar will begin to form clumps, but that’s okay. Just keep whisking and as it continues to cook, they will melt back down. Stop whisking once all of the sugar has melted, and swirl the pan occasionally while the sugar cooks.

Continue cooking until the sugar has reached a deep amber color. It should look almost a reddish-brown, and have a slight toasted aroma. This is the point where caramel can go from perfect to burnt in a matter of seconds, so keep a close eye. If you are using an instant-read thermometer, cook the sugar until it reaches 350° F.

As soon as the caramel reaches 350°F, add the butter all at once. Be careful, as the caramel will bubble up when the butter is added. Whisk the butter into the caramel until it is completely melted.

Remove the pan from the heat and slowly pour the cream into the caramel. Again, be careful because the mixture will once again bubble up ferociously. Whisk until all of the cream has been incorporated and you have a smooth sauce. Add the whiskey and fleur de sel and whisk to incorporate.

Set the sauce aside to cool for 10 to 15 minutes and then pour into your favorite glass jar and let cool to room temperature. You can refrigerate the sauce for up to 2 weeks


Guinness Black Magic Cake brought to you by: Runcible Temps (

Links to Useful Kitchen Tools & Ingredients for Guinness Black Magic Cake:

OXO Good Grips Stainless Steel Food Scale

Kitchen Aid Stand Mixer

Thermoworks Super-Fast Thermapen Cooking Thermometer

Le Creuset Enameled Cast Iron Sauce Pan

Chicago Metallic Non-Stick 8 – inch round cake pan

5 Responses to Guinness Black Magic Cake

  1. Piglove says:

    Did you hear that noise? It was the sound of my little piggy butt passing out with a THUD. That cake looks amazing! I would love to have a nibble or three please and thanks. XOXO – Bacon

  2. tanya2austin says:

    This is my favorite frosting too! Except the recipe I use also has a little cornstarch in it, and instead of beating the butter and adding the roux in a little at a time, you beat the roux (which has the sugar melted in already) and add the butter in a little at a time so it emulsifies better. I find that the first method tends to result in a curdled frosting sometimes, which drives me nuts!

    • liadh1 says:

      Your frosting method definitely sounds interesting. I’ll have to look into it. The Ermine frosting was a huge hit around here so I’m sure I will be making it again! best-Lea

  3. hocuspocus13 says:

    Reblogged this on hocuspocus13 and commented:

  4. Aurelie says:

    This. Looks. Obscenely. Delicious.

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