There are some desserts that feel like a moment. Not just something sweet you eat, but something that slows you down, makes the kitchen smell incredible, and gives you an excuse to pour a little something special while you bake. This Guinness chocolate cake is exactly that kind of dessert.

If you’ve never baked with Guinness before, I promise - you’re not making a “beer cake.” You’re making a deep, rich, unbelievably moist chocolate cake that just happens to have Guinness in it. The stout brings out the chocolate flavor in a way that coffee lovers understand instinctively. It doesn’t taste boozy, it doesn’t taste bitter - it just tastes more chocolatey.

And then there’s the frosting. Oh, the frosting. This Irish buttercream is creamy, lightly sweet, and so smooth it practically melts when it hits the cake. It’s made with Irish butter, which if you know, you know. There’s something about it that’s richer and more indulgent without being heavy.

This is the cake I make when:

I want something impressive but comforting
I’m baking for St. Patrick’s Day but don’t want green food coloring
I want a dessert that people ask for the recipe for
Or I just want to bake something that feels a little special

Let’s talk about why this cake works so well and then I’ll walk you through exactly how to make it.

Why Guinness Works in Chocolate Cake

At first glance, Guinness in a cake sounds… questionable. But stout beers are actually incredible for baking, especially with chocolate. Guinness has notes of coffee, cocoa, and malt, which deepen the flavor of the chocolate without overpowering it.

When you cook the Guinness down slightly with butter, it loses any harsh edge and becomes smooth and almost creamy. That mixture goes straight into the batter, giving you:

A darker, richer crumb
Moist texture that stays soft for days
Chocolate flavor that tastes bakery-level

This cake is not overly sweet, which is exactly why the buttercream on top works so beautifully.

Ingredients

For the Guinness Chocolate Cake

For the Irish Buttercream Frosting

Instructions for the Cake

Step 1: Preheat and Prep

Preheat your oven to 350°F (175°C). Grease and line two 8-inch round cake pans or one tall 9-inch pan, depending on how you want to layer it.

Step 2: Heat the Guinness and Butter

In a saucepan over medium heat, combine the Guinness and butter. Stir until the butter is fully melted. Remove from heat and whisk in the cocoa powder until smooth. Set aside to cool slightly.

This mixture will smell incredible - deep, chocolatey, and rich.

Step 3: Mix the Dry Ingredients

In a large bowl, whisk together the flour, sugar, baking soda, and salt.

Step 4: Add the Wet Ingredients

In a separate bowl, whisk together the eggs and sour cream until smooth. Slowly pour in the cooled Guinness mixture, whisking gently.

Step 5: Combine

Pour the wet ingredients into the dry ingredients and mix just until combined. The batter will be thin - that’s exactly what you want.

Step 6: Bake

Pour the batter into your prepared pan(s). Bake for 40–45 minutes, or until a toothpick inserted in the center comes out clean.

Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

Instructions for the Irish Buttercream Frosting

Step 1: Beat the Butter

In a large bowl, beat the softened Irish butter until light and creamy.

Step 2: Add Sugar

Gradually add the powdered sugar, one cup at a time, beating well after each addition.

Step 3: Finish the Frosting

Add vanilla, salt, and cream. Beat until smooth and fluffy. Adjust the consistency as needed - thicker for piping, softer for spreading.

Assemble the Cake

Once the cake is completely cool:

Spread or pipe frosting between layers
Frost the top and sides
Add simple swirls or keep it rustic

This cake is beautiful without being perfect.

Let’s Talk About the Irish Buttercream

This frosting deserves its own moment.

Irish butter has a higher butterfat content than standard butter, which makes the buttercream:

Extra smooth
Rich without being greasy
Perfectly pipeable or spreadable

The frosting is lightly sweetened so it doesn’t overpower the cake. Think silky, creamy, and balanced - the kind of frosting people scrape off the plate with their fork when they think no one’s watching.

What You’ll Love About This Cake

It’s easy to make, even if you don’t bake often
No fancy techniques or special equipment
Perfect for holidays, birthdays, or dinner parties
Stays moist for days
Looks beautiful with minimal decorating

It’s the kind of cake that feels elevated but still totally approachable.

Tips for Success

Let the Guinness mixture cool slightly before adding eggs
Don’t overmix the batter
Use room temperature ingredients for smooth frosting
Chill the cake briefly if frosting feels too soft

How to Store

Store covered at room temperature for 1 day
Refrigerate up to 4 days
Bring to room temperature before serving for best texture

Perfect for St. Patrick’s Day (Without Being Gimmicky)

This cake feels festive without relying on green food coloring or novelty decorations. It’s rich, cozy, and elegant - exactly the kind of dessert people remember.

If you make one dessert this season, let it be this one.

And if you do bake it, don’t be surprised when someone asks if you sell this cake. It happens

Looking for more St Patricks Day recipes? Try my popular recipes below:

Guinness Chocolate Cake with Irish Buttercream Frosting