Step 1: Preheat your oven to 350°F (175°C). This ensures your cake bakes evenly.
Step 2: Grease your 9x13 inch baking pan with butter or non-stick spray. If you prefer, you can line the bottom with parchment paper for easier removal.
Step 3: In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt until well combined.
Step 4: In another bowl, combine the milk, vegetable oil, eggs, and vanilla extract. Mix until well blended.
Step 5: Pour the wet mixture into the dry ingredients. Mix until just combined. Don’t worry about small lumps; it’s important not to over-mix.
Step 6: Carefully stir in the boiling water. The batter will be thin, but that’s okay! This will help create a moist cake.
Step 7: Pour the batter into your prepared baking pan. Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted in the center comes out clean.
Step 8: Once baked, remove the cake from the oven and let it cool in the pan for 10 minutes. Then transfer it to a cooling rack to cool completely.
Step 9: In a mixing bowl, beat the softened butter and cocoa powder until well combined. Gradually add the sifted powdered sugar, vanilla extract, and a pinch of salt. Mix until smooth, adding half and half as needed to reach your desired consistency.
Step 10: Once the cake is completely cool, spread the frosting evenly over the top. Feel free to get creative with your frosting technique!