Preparation Steps

• Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.
• In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, and salt.
• In a separate bowl, combine the buttermilk, oil, eggs, and vanilla extract. Add to the dry ingredients and mix until just combined.
• Gradually add the boiling water to the batter and mix until smooth. Pour the batter into the prepared pan and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
• Let the cake cool completely before frosting. To make the filling, beat the butter until smooth and creamy. Gradually add the powdered sugar, alternating with the milk and vanilla extract, until the filling is light and fluffy.
• Cut the cake into squares or circles. Spread a generous amount of frosting on half of the cake pieces, then top with the remaining cake pieces to form sandwiches.