• Preheat the oven to 350°F (175°C).
• Grease and line three 9-inch round cake pans with parchment paper.
• In a large bowl, whisk together sugar, flour, cocoa powder, espresso powder, baking soda, baking powder, and salt.
• Add eggs, buttermilk, sour cream, oil, and vanilla extract.
• Beat with a hand mixer on medium speed until smooth.
• Slowly pour in boiling water while mixing on low speed; batter will be thin.
• Divide batter evenly between pans.
• Bake for 28–32 minutes or until a toothpick inserted comes out clean.
• Cool in pans for 10 minutes, then transfer to wire racks to cool completely.

Make the Cake Soak

• In a small saucepan, stir together water, cocoa powder, sugar, and vanilla extract.
• Heat over medium heat just until sugar dissolves.
• Remove from heat and let cool.

Make the Chocolate Frosting

• Beat softened butter in a large bowl until creamy.
• Add cocoa powder and mix until fully blended.
• Gradually add powdered sugar, alternating with milk.
• Mix in vanilla extract.
• Beat until light, fluffy, and spreadable.

Assemble the Cake

• Place one cake layer on a serving plate or cake stand.
• Brush the top with a few spoonfuls of cake soak.
• Spread a generous layer of chocolate frosting over the top.
• Repeat with the second and third layers, soaking and frosting each.
• Cover the top and sides of the cake with the remaining frosting.

Serve

• Let cake sit for 30 minutes before slicing.
• For a firmer frosting, chill before serving.
• Slice big and enjoy, Matilda-style!