The party table isn’t complete without a chocolate sheet cake for everyone to grab. This festkake (party cake) is a classic – the dark horse among all the vanilla layer cakes, almond wreath cakes, and pavlovas. It’s rich, sweet, and tantalizing for kids and adults alike.

As Norway’s Constitution Day approaches, it seems fitting to share this favorite that’s adorned with a smooth and fluffy buttercream and color-appropriate sprinkles. I’ve had my fair share of chocolate cakes, but this one is by far my favorite. It’s incredibly moist, but not dense and heavy, and while it’s sweet, it’s not overly sweet. The buttercream is soft and creamy, not grainy or crumbly. It’s also so simple to pull this cake together and you can decorate as you see fit.

Serving it as a sheet cake inevitably extends the invitation for sharing, which is really what the festivities are all about.

Moist Chocolate Sheet Cake (sjokoladekake i langpanne)

Serves 15 to 20

For the cake:

• 1 cup (224 g) lightly salted butter
• ¾ cup (75 g) cocoa powder  
• 2 cups (240 g) all-purpose flour
• 2 ¼ teaspoons baking soda
• ½ teaspoon baking powder
• 1 teaspoon salt
• 1 ¾ cups (350 g) granulated sugar
• 2 large eggs, at room temperature
• 1 ½ cups (360 ml) lukewarm water
• 1 ¼ cup (300 ml) buttermilk (kulturmelk)

For the frosting:

• 1 cup (224 g) lightly salted butter
• 2 cups (240 g) confectioners’ sugar
• ½ cup (50 g) cocoa powder
• 6 tablespoons heavy cream
• 1 teaspoon vanilla
• Sprinkles, to serve

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Preheat the oven to 350°F (180°C). Butter a 13 x 9 inch (33 x 23 cm) cake pan.

In a small saucepan, melt the butter over low heat. Pour the melted butter into a large bowl. Whisk in the cocoa powder and set aside to cool slightly.

In a medium bowl, whisk together the flour, baking soda, baking powder, and salt.

When the butter and cocoa mixture has cooled, whisk in the granulated sugar and eggs.  Add the lukewarm water and buttermilk and beat together. Add the flour mixture and beat until well blended (I like to use electric whisks at this point and mix for 2 minutes, but you can also whisk by hand). Pour the batter into the prepared pan. Bake for 30 minutes, or until a toothpick inserted in the center comes out clean. Cool completely in the pan.

For the frosting, in the bowl of a stand mixer fitted with the paddle attachment, beat the butter, confectioners’ sugar, and cocoa powder for 1 minute, or until light and fluffy. Add the heavy cream and vanilla, and beat until well blended and smooth. Spread the frosting over the cake and top with sprinkles, if using. Serve immediately or keep covered in the refrigerator for up to 4 days.

You can also freeze the cake with or without the frosting. Wrap the cake well in plastic and then cover in foil. Freeze for up to 3 months and allow the cake to thaw completely before serving.

*For more 17 May cake inspiration, click here.