Ingredients:

  • 2 cups All-Purpose Flour (spooned and leveled)
  • 2 cups Granulated Sugar
  • 1 teaspoon Baking Soda
  • 1/2 teaspoon Salt (fine sea salt preferred)
  • 1 cup Unsalted Butter (cubed)
  • 1 cup Unsweetened Cocoa Powder (good quality)
  • 1 cup Boiling Water (freshly boiled)
  • 1 cup Buttermilk (room temperature)
  • 2 Large Eggs (lightly beaten)
  • 1 teaspoon Vanilla Extract (for cake)
  • 1/2 cup Unsalted Butter (for glaze)
  • 1/2 cup Unsweetened Cocoa Powder (for glaze)
  • 1/3 cup Milk (whole or 2%)
  • 4 cups Powdered Sugar (sifted if lumpy)
  • 1 teaspoon Vanilla Extract (for glaze)
  • 1 cup Chopped Pecans or Walnuts (Optional, for topping)

Instructions:

  1. Preheat oven to 350°F (175°C). Generously grease a 15x10 inch (approx. 38cm x 25cm) jelly roll or half-sheet pan.
  2. In a large bowl, whisk together the flour, sugar, baking soda, and salt. Set aside.
  3. In a saucepan, combine the cubed butter, cocoa powder, and the boiling water. Heat over medium heat, stirring constantly until the butter is melted and the mixture is smooth and glossy. Remove immediately from heat.
  4. Whisk the hot chocolate mixture into the dry ingredients until just combined. Do not overmix.
  5. In a separate small bowl, whisk the buttermilk, eggs, and vanilla together. Gently fold this wet mixture into the chocolate batter until uniform.
  6. Pour the thin batter evenly into the prepared pan and bake for 20–25 minutes. A toothpick inserted near the centre should come out with a few moist crumbs attached.
  7. During the last 5 minutes of baking, prepare the glaze: In the saucepan (cleaned if necessary), combine the butter (for glaze), cocoa powder (for glaze), and milk. Bring to a gentle simmer over medium heat, stirring until smooth. Remove from heat.
  8. Immediately whisk the powdered sugar and vanilla into the hot chocolate mixture until smooth and glossy. If using nuts, stir them in now.
  9. While the cake is still hot in the pan, immediately pour the warm glaze evenly over the entire surface. If using nuts, sprinkle them quickly over the wet glaze.
  10. Allow the cake to cool completely at room temperature before slicing and serving so the glaze can set.