Step 1: Preheat and Prepare Pans
Preheat oven to 350°F (175°C). Grease two 9-inch round cake pans with butter or cooking spray. Line bottoms with parchment paper rounds, then grease the parchment. Dust lightly with cocoa powder (instead of flour) for chocolate cakes, tapping out excess. Set aside.

Step 2: Mix Dry Ingredients
In a large mixing bowl, whisk together flour, sugar, cocoa powder, baking soda, baking powder, and salt. Whisk thoroughly for at least 30 seconds to ensure everything is well combined and there are no lumps in the cocoa powder. This is important for even distribution of leavening agents.

Step 3: Add Wet Ingredients
Add eggs, milk, oil, and vanilla extract to the dry ingredients. Using a whisk or electric mixer on medium speed, beat until well combined and smooth, about 2 minutes. The batter will be thick at this point. Scrape down the sides of the bowl to ensure everything is incorporated.

Step 4: Add Hot Coffee
Carefully stir in the hot coffee (or hot water). The batter will become very thin – don’t worry, this is correct! The thin batter creates the incredibly moist texture. Mix just until combined. The batter should be smooth and pourable, like thick hot chocolate consistency.

Step 5: Divide and Bake
Divide batter evenly between prepared pans (use a kitchen scale for precision – about 650g per pan). Tap pans gently on counter 2-3 times to release air bubbles.

Bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs (not wet batter). The cake should spring back when lightly touched. Don’t overbake or the cake will be dry!

Step 6: Cool Completely
Remove from oven and let cakes cool in pans on wire racks for 10 minutes. Run a knife around the edges, then carefully invert onto wire racks. Peel off parchment paper. Flip cakes right-side up and cool completely before frosting – at least 1-2 hours. This is crucial!

Step 7: Make Chocolate Buttercream (Optional)
Beat softened butter on medium speed until creamy, about 2 minutes. Add cocoa powder and beat until smooth. Gradually add powdered sugar, one cup at a time, alternating with heavy cream. Add vanilla and salt. Beat on high speed for 3 minutes until light and fluffy. If too thick, add more cream; if too thin, add more powdered sugar.

Step 8: Assemble and Frost
Level cake tops if domed (use serrated knife). Place one layer on serving plate. Spread about 1 cup frosting on top. Place second layer on top. Apply thin “crumb coat” of frosting over entire cake. Refrigerate 15 minutes until firm. Apply final coat of frosting, smoothing with offset spatula or bench scraper.

Step 9: Serve and Enjoy
Let frosted cake sit at room temperature 30 minutes before slicing for easiest cutting and best flavor. Slice with a sharp knife, wiping clean between cuts. Store any leftovers covered at room temperature or refrigerated.