The Best Chocolate Sheet Cake – Easy One-Pot Recipe 🍫✨

• ### For the Cake
• 6 tbsp (85g) unsalted butter
• 3 oz (85g) chopped dark chocolate
• 1/4 cup (25g) unsweetened cocoa powder
• 1/2 cup (120ml) brewed coffee
• 1 1/2 cups (300g) granulated sugar
• 1/2 tsp (3g) kosher salt
• 1 tsp (5ml) vanilla extract
• 1/2 cup (120ml) buttermilk
• 2 large eggs
• 1 1/4 cups (155g) all-purpose flour
• 1 tsp (5g) baking powder
• 1/2 tsp (2g) baking soda
• ### For the Chocolate Buttercream
• 6 tbsp (85g) unsalted butter, softened
• 1/4 cup (25g) unsweetened cocoa powder
• 1/4 tsp (1g) kosher salt
• 1 tsp (5ml) vanilla extract
• 2 cups (240g) powdered sugar
• 3–4 tbsp (45–60ml) heavy cream
• ### For the Pourable Fudgy Icing (Alternative)
• 14 tbsp (198g) unsalted butter
• 1/4 cup heaping (30g) unsweetened cocoa powder
• 1/4 tsp (1g) kosher salt
• 6 tbsp (90ml) milk
• 1 tsp (5ml) vanilla extract
• 3 cups (360g) powdered sugar

Instructions

1. 1

   Preheat the oven to 350°F (175°C). Line a large rimmed baking sheet with parchment paper, allowing the sides of the parchment to overhang so that the cake can be easily lifted out after it's baked. I'm using a 13x18 inch (33x46cm) half sheet, which is ideal for this cake, but a regular jelly roll rimmed baking sheet will work.

2. 2

   Melt the butter over low heat in a medium pot. Once melted, remove from heat. Add the chopped chocolate and allow it to sit for a minute. Then stir with a rubber spatula until the chocolate has melted. Add the cocoa powder and stir until smooth.

3. 3

   Mix in the coffee, sugar, salt, and vanilla with a whisk. You do not need to let this mixture cool completely; however, allowing it to cool down a little bit is a good idea.

4. 4

   Add the buttermilk and eggs, making sure to whisk well immediately after adding them to gradually warm the eggs and ensure they do not scramble in your still-warm chocolate mixture.

5. 5

   Sift the flour combined with baking powder and baking soda directly into your batter. Mix it with a whisk until completely combined. Then mix with a few more vigorous strokes of a whisk to aerate the batter a bit.

6. 6

   Pour the batter into the prepared baking sheet. Bake in the preheated oven for about 20 minutes until the cake is firm and a toothpick inserted in the centre comes out with just a few crumbs but not wet or liquid batter. If you press down on the cake, your finger should still be able to leave an indentation, a sure sign your cake is plenty gooey and not overbaked. The internal temperature measure that I love to use with baking will not work as well here, since the cake is so thin and the reading may not be accurate – a toothpick will work just fine! Remove the cake from the oven and allow it to cool completely before icing.

7. 7

   In the bowl of a stand mixer, mix all of the icing ingredients on low at first to avoid all of the sugar and cocoa from splashing everywhere. When everything is incorporated, increase the speed to high and beat for a few minutes until fluffy and lightened in colour. Remember to adjust the consistency of the buttercream with more heavy cream, if needed. Stop the mixer, scrape the sides of the bowl, and beat on high for another minute or two. Lift the cooled cake out of the pan by the sides of the parchment paper. Spread two-thirds of the buttercream evenly over the cake. Pipe the remainder of the icing in a decorative manner, if desired. Slice the cake into the desired number of squares; I sliced mine into 32.

8. 8

   In a medium saucepan, melt the butter over low heat; remove from heat once melted. Add the cocoa powder and stir. Stir until it forms a thick ganache-like concoction. Add the salt, milk, vanilla, and powdered sugar. Whisk well to combine. The consistency should be thick but pourable; if your icing is too thin, you may need to add a bit more powdered sugar. Pour over your cooled or still-warm sheet cake. Feel free to add chopped toasted walnuts or pecans for another layer of texture and flavour. It's so delicious!