Texas Chocolate Quarter Sheet Cake

Preheat your oven to 350°F (175°C).
Lightly grease a quarter-sheet pan (12×10 inches) with cooking spray.
Make the Cake:

In a medium mixing bowl, whisk together the flour, sugar, and salt.
In a small saucepan, melt the butter over medium-low heat.
Once melted, stir in the cocoa powder and boiling water until smooth.
In a measuring cup, combine the buttermilk, egg, baking soda, and vanilla extract.
Add the buttermilk mixture to the flour mixture, followed by the hot water mixture.
Stir until well combined and pour the batter into the prepared pan.
Bake for 15 to 18 minutes, or until a toothpick inserted into the center comes out clean.
Make the Frosting:

While the cake is baking, melt the butter in the same saucepan over medium-low heat.
Stir in the cocoa powder, buttermilk, and vanilla extract, and bring to a simmer.
Remove from heat and whisk in the sifted powdered sugar until smooth.
Frost the Cake:

Once the cake is done, remove it from the oven and allow it to cool for 30 minutes.
Pour the frosting over the warm cake and spread evenly to the edges with an offset spatula.
Serve and Enjoy:

Let the cake cool completely before serving. Enjoy the moist, chocolatey goodness!
Serving and Storage Tips: