• Preheat your oven to 350°F (175°C). Grease two 9-inch round pans and line them with parchment paper.
• In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt until well combined.
• Add the milk, vegetable oil, eggs, and vanilla extract to the dry ingredients. Whisk until smooth.
• Carefully stir in the boiling water until the batter is well combined; the batter will be thin.

Baking

• Pour the batter evenly into the prepared pans.
• Bake for 30-35 minutes. Check for doneness with a toothpick.
• Let the cakes cool in the pans for 10 minutes, then invert onto cooling racks.

Frosting Preparation

• Beat together the softened butter, cocoa powder, powdered sugar, vanilla extract, and salt.
• Gradually add milk until the frosting reaches a spreadable consistency.

Assembly

• Place one cake layer on a cake stand and spread about 1 cup of frosting on top.
• Add the second layer and frost the top and sides of the cake.

Serving

• Serve the cake immediately or store it covered at room temperature.