01 - Preheat the oven to 350°F. Grease and flour two 9-inch round cake pans, then line the bottoms with parchment paper for easy release.
02 - In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt until thoroughly blended.
03 - Add the eggs, milk, vegetable oil, and vanilla extract to the dry mixture. Beat on medium speed with an electric mixer until fully incorporated, about 2 minutes.
04 - Carefully stir in the boiling water by hand—the batter will become thin and watery, which is normal and essential for a moist cake.
05 - Divide the batter evenly between the prepared pans. Bake for 30 to 35 minutes, or until a wooden toothpick inserted into the center comes out clean.
06 - Let the cakes cool in the pans for 10 minutes, then carefully invert onto wire racks to cool completely before frosting.
07 - Beat the softened butter in a large bowl until creamy and smooth. Sift in the cocoa powder and mix until fully incorporated.
08 - Gradually add the powdered sugar, alternating with the milk, mixing on low speed until smooth. Add the vanilla extract and pinch of salt, then beat on medium-high until fluffy and spreadable. Add additional milk 1 tablespoon at a time if needed.
09 - Place one cooled cake layer on a serving plate. Spread an even layer of frosting over the top. Stack the second layer on top.
10 - Cover the top and sides of the cake with the remaining frosting. Use an offset spatula to create dramatic swoops and swirls for the signature Matilda look.