Start by mixing together the cocoa powder, sugar, and cornstarch in a medium-sized saucepan. This is where you'll build the foundation of flavor. Give it a good stir to eliminate any lumps.

Next, pour in 1 ½ cups of the whole milk. Whisk the mixture until smooth. This is your moment to incorporate all the flavors together. Place the saucepan over medium heat, stirring consistently.

Bring the mixture to a gentle boil. As it heats, keep stirring. You’ll start to notice it thickening beautifully. Once it reaches a boil, reduce the heat and let it simmer for about two minutes.

In a bowl, whisk the egg yolks together. Take a small amount of the hot mixture and slowly pour it into the yolks while whisking constantly. This prevents the eggs from scrambling. Once blended, whisk this back into the saucepan with the remaining milk.

Continue to cook over low heat until everything is combined and thickened. It should take about 5 minutes longer. Stir in the butter, chocolate extract, and cinnamon. At this point, your kitchen should smell divine.

Once thickened, remove the saucepan from heat. Transfer the pudding into serving bowls or a single dish for chilling. Cover with plastic wrap directly on the surface (this avoids a skin forming). Chill for at least two hours in the fridge before serving.