Preheat your oven to 350°F (175°C). Grease your 9x13 inch baking pan with butter or cooking spray to ensure easy removal.
In a large mixing bowl, whisk together 2 cups of all-purpose flour, 2 cups of sugar, and 1 teaspoon of salt until combined.
In a saucepan over medium heat, melt 1 cup of unsalted butter. Add 4 heaping tablespoons of unsweetened cocoa powder, stirring until well blended.
Pour in 1 cup of boiling water to the chocolate mixture and stir until smooth. Remove from heat.
In another bowl, mix together ½ cup of buttermilk, 2 beaten eggs, 1 teaspoon of baking soda, and 1 teaspoon of pure vanilla extract.
Slowly pour the chocolate mixture into the dry ingredients, mixing gently. Next, add the buttermilk mixture and combine until just blended.
Pour the batter into the prepared pan and bake for 20–25 minutes, or until a toothpick inserted in the center comes out clean.
While the cake is baking, make the frosting. In a saucepan, melt ¼ cup of unsalted butter. Stir in 4 heaping tablespoons of cocoa powder and 6 tablespoons of milk. Bring to a gentle boil, and then remove from heat.
Add 1 pound of confectioners' sugar and 1 teaspoon of vanilla extract to the chocolate mixture. Stir until smooth.
Once the cake is baked and cooled, pour the frosting over the top, spreading it evenly. Sprinkle 1 cup of chopped pecans on top for that extra crunch.
