01 -
Preheat oven to 350°F and grease a half sheet pan (13x18 inches) with nonstick spray. Set aside.
02 -
In a large mixing bowl, stir together the flour, sugar, and salt. Set aside.
03 -
In a saucepan over medium heat, melt the butter. Whisk in cocoa powder until thoroughly combined. Stir in boiling water and increase heat to medium-high. Bring to a boil and let boil for 30 seconds. Immediately turn off heat.
04 -
Pour hot cocoa powder mixture over the flour mixture and stir to mix, scraping the bottom and sides well.
05 -
In a medium bowl, whisk together the buttermilk, eggs, baking soda, and vanilla extract.
06 -
Stir the buttermilk mixture into the chocolate and flour mixture until fully combined.
07 -
Pour batter into the prepared baking sheet. Bake until the top springs back lightly and edges start to come away from the sides, about 15-20 minutes.
08 -
In a saucepan over low heat, melt the butter. Once melted, whisk in cocoa powder.
09 -
Whisk in milk, vanilla, and powdered sugar until fully incorporated and smooth. Remove from heat and stir in chopped pecans.
10 -
Pour frosting over the warm cake, and use an offset spatula to spread it to the edges.
11 -
Let the cake cool until the frosting sets. Slice and serve.