To make the cake batter:In a small, stainless steel saucepan, combine milk and cocoa powder together and bring to a boil over medium-high heat, whisking frequently. Remove from heat and let come to room temperature.
Add the flour and mix on low for about 15 seconds; then, increase speed to medium and mix for about 45-60 seconds. Add the cooled cocoa mixture and mix on medium speed just until combined.