Step 1 – Prepare Your Pan & Oven

Preheat your oven to 350°F (175°C). Grease and flour a 10×15 inch sheet pan. This size helps create that classic thin layer with just the right amount of richness per bite.

Step 2 – Make the Cake Batter

In a large mixing bowl, combine the flour, sugar, baking soda, and salt. Stir together.

Now beat in the sour cream and eggs until the mixture is smooth and well combined.

Meanwhile, in a saucepan over low heat, melt 1 cup of butter. Add 1 cup of water and 5 tablespoons of cocoa powder, stirring to combine. Bring this mixture to a gentle boil, then remove it from the heat and let it cool slightly.

Pour the cocoa mixture into the flour and egg mixture. Stir well until everything is blended into a luscious, chocolatey batter.

Step 3 – Bake

Pour the batter into your prepared sheet pan and bake in the preheated oven for about 20 minutes, or until a toothpick inserted into the center comes out clean. Do not overbake — you want that signature soft and moist texture.

Step 4 – Prepare the Frosting

While the cake is baking (or immediately after), start your frosting.

In a large saucepan, combine:

• • 6 tablespoons milk

• • 5 tablespoons cocoa powder

• • ½ cup butter

Bring the mixture to a boil, then remove from heat.

Stir in 4 cups of confectioners’ sugar and 1 teaspoon of vanilla extract. Mix until smooth. If desired, fold in 1 cup of chopped walnuts for a crunchy, nutty finish.

Step 5 – Frost While Warm

Here’s the magic: Spread the warm frosting over the warm cake. This allows the icing to seep into the top layer of the cake slightly, creating a rich, fudgy topping that blends perfectly into every bite.

Let the cake cool slightly before serving — or serve warm for extra indulgence!