Brownie Picnic Cake with Chocolate Buttercream Frosting
Brownie Picnic Cake with Chocolate Buttercream Frosting

Brownie Picnic Cake with Chocolate Buttercream Frosting is a throwback to the cakes your grandmother made for family gatherings. We love this easy make-and-take cake for summer picnics or parties!

Summer is officially in full swing! Our favorite meal for entertaining or a family gathering includes juicy burgers topped with lots of cheese, grilled brats, Dutch Oven Molasses Baked Beans,  Aunt Di’s  Potato Salad, fresh fruit, Fresh Squeezed Lemonade and corn on the cob topped with Chile Lime and Garlic Flavored Butter. Last, but not least, Brownie Picnic Cake with Chocolate Buttercream Frosting is the perfect way to feed a crowd dessert!  Homemade brownie cake will take your party to a new level. There’s nothing quite like a cake made with quality ingredients and love. I’m teaming up with  Kerrygold  butter and Martha Stewart Living to bring you this amazingly rich and moist cake that will leave a lasting impression on everyone!

Kerrygold Butter from Irish Cows

Brownie Picnic Cake with Chocolate Buttercream Frosting

The first time I tasted Kerrygold butter was several years ago while traveling in China. I was staying with my friend Leanne in Shanghai, along with my daughter Brookie. Leanne bought some Kerrygold butter with a loaf of bread for us to eat for breakfast. We ate the whole loaf of bread (had to go buy another loaf) and most of the butter while we stayed at her home for 4 days. Where is my hide-the-face emoji?!  I could taste the difference right away. I couldn’t quite put my finger on it, but I could tell Kerrygold butter was better than the butter I was eating at home. A little research turned up this information: Kerrygold butter comes from the milk of grass-fed cows that are free of growth hormones. The unsalted version of their butter is an all-natural Irish butter. You can taste the difference when you compare Kerrygold butter to butter made in the U.S. Kerrygold butter is higher in butterfat content than most butter which makes it perfect for baking!  The color, texture and flavor are completely different than any other butter you’ve tasted.

The perfect combo

Brownie Picnic Cake with Chocolate Buttercream Frosting

This cake combines butter, buttermilk, sugar  and unsweetened melted chocolate to make a cake that has the texture of a light brownie without being too cakey. The butter and buttermilk combo makes it extra moist and rich. I served my Brownie Picnic Cake with Chocolate Buttercream Frosting on this cute plate from one of my favorite collections, “Whim” from Martha Stewart. So fun for any occasion!

Salted vs unsalted

I’m often asked if I use salted or unsalted butter in my baked goods. I always purchase unsalted butter for a few reasons. First, I like to know exactly how much salt is going into my baking. The amount of salt added to  regular, salted butter varies from brand to brand. If I add my own salt, I have control over the salt in the recipe and know how it will taste when I’m ready to serve, no guess work involved! Second, taste tests conducted by various sources say that unsalted butter produces better tasting baked goods. I cannot agree more! I consistently get better results when I bake with unsalted butter, which is the reason I only purchase unsalted butter for all of our baking and cooking needs.

Brownie Picnic Cake with Chocolate Buttercream Frosting
Brownie Picnic Cake with Chocolate Buttercream Frosting

Brownie Picnic Cake with Chocolate Buttercream Frosting- the perfect dessert for any occasion

Traditionally, the definition of a picnic cake is a simple cake that travels well (usually made in a 9×13 pan) and does not require frosting to be enjoyed. I topped my Brownie Picnic Cake with Chocolate Buttercream Frosting because I know most people love a good layer of chocolate frosting on their cake! Nothing caps off a meal quite like a slice of dense, moist chocolate cake. If you’ve been looking for a cake that is easy to put together and stays moist for days, this is your cake!  I love to serve it without frosting, topped with a large scoop of vanilla ice cream. I also love Brownie Picnic Cake with Chocolate Buttercream Frosting served chilled, straight from the fridge! It’s  a great treat for a hot summer day when served cold.  Hope you enjoy this cake as much as we do! I’m guessing it will become one of your family favorite recipes. Make sure to check the recipe notes for helpful tips and for more recipes!

Thanks to Kerrygold  and Martha Stewart Living for sponsoring this post

Brownie Picnic Cake with Chocolate Buttercream Frosting

Brownie Picnic Cake with Chocolate Buttercream Frosting

5 from 2 votes
Author: Si Foster
Prep Time: 15 minutes
Cook Time: 40 minutes
Total Time: 55 minutes
Servings: 20 -24 serving



  • 1/2 cup water, heated
  • 3 oz unsweetened chocolate, chopped
  • 1 cup Kerrygold unsalted butter, cut into tablespoons at room temperature
  • 2 1/4 cups granulated sugar
  • 2 eggs
  • 1 cup shaken buttermilk
  • 2 teaspoons vanilla
  • 2 cups all purpose flour
  • 1 teaspoon salt
  • 1/2 teaspoon baking soda

buttercream frosting:

  • 1/2 cup Kerrygold unsalted butter, cut into tablespoons
  • 2-3 oz unsweetened chocolate, chopped and melted* or 1/3 cup unsweetened cocoa powder
  • 4 cups powdered sugar
  • 2 dashes of salt
  • 1 teaspoon vanilla
  • 2-3 tablespoons milk or cream


  • Place rack in center of oven and preheat oven to 350 degrees.
  • Microwave water for one minute in a bowl. Add 3 oz chopped unsweetened chocolate and stir with a fork or whisk until smooth. Set aside.
  • Place room temperature butter in a mixing bowl or in the bowl of a stand mixer. Turn the mixer on and cream butter and sugar until smooth.
  • Add eggs and beat for one minute. Add buttermilk and vanilla mix until smooth.
  • Add the melted chocolate mixture to the wet ingredients.
  • Add flour, salt, baking soda all at once to bowl. Pulse the mixer until the ingredients are incorporated. When the dry ingredients have disappeared, turn the mixer to medium and mix for one minute.
  • Grease a 9×13 pan with cooking spray. Scrape the batter into the pan and bake for 35-40 minutes*

Prepare frosting while cake is baking:

  • Place butter, cut into tablespoons in a large mixing bowl. Add melted chocolate or cocoa powder, beat for one minute.
  • Add powdered sugar, salt and vanilla. Mix, adding in milk or cream until smooth. See recipe notes for tips.
  • When cake is cooled completely, spread frosting on top and serve.


  • Kerrygold butter is softer than most butter because it has a higher butterfat content. It is usually quite soft when removed from the refrigerator. If the butter needs to be softened up a bit, remove from the foil packaging and place on a plate. Let sit at room temperature for about 30 minutes.
  • You may use unsweetened solid chocolate bars or unsweetened cocoa powder in this recipe. I prefer unsweetened solid chocolate to cocoa powder in this recipe. To melt the chocolate, place in a bowl and microwave for 15 seconds at a time until melted. Chocolate burns quite quickly in the microwave, so only cook for a few seconds at a time.
  • Baking time may vary on this cake. It is meant to be a dense, moist, brownie-like cake. It should rise up as a cake would, but not quite as much as a traditional cake. Sifting the flour will produce a lighter and taller cake. If you prefer the finished product to be taller, sift the flour and bake at 375 for about 25-30 minutes.
  • Because the cake is dense, it may sink a bit in the middle and have taller outer edges. No worries! I simply use a silicone spatula or wood spatula and press the outer edges down so they are even with the center of the cake for an even finish. Do this while the cake is hot out of the oven!

Did you make this recipe?

Be sure to leave a comment and give this recipe a rating, letting me know how you liked it. I’d love to see a photo, tag @abountifulkitchen on Instagram!