In a medium saucepan over medium heat, combine the unsalted butter, dark brown sugar, coconut sugar, and salt. Stir continuously until melted and smooth. Be patient. Once all the sugars have dissolved and the mixture is bubbling, let it simmer for about 2 minutes, which allows for that deep, toasty flavor to develop.
In another bowl, whisk together your milk and half & half. In a small bowl, mix cornstarch with a tablespoon of this milk and set aside. In another bowl, whisk your egg yolks until pale, then add to the remaining milk mixture along with the malted milk powder, white miso, scraped vanilla bean, maple syrup, and Scotch whisky.
Once your butterscotch has cooled slightly, combine with the milk mixture in the saucepan, bringing everything to a gentle simmer over medium heat. Stir constantly to prevent any curdling.
Add the cornstarch mixture to your custard. Keep stirring until the pudding thickens, typically around 5-7 minutes. It’s crucial here—I remember the satisfaction when the pudding finally reached that perfect velvety consistency.
Remove from heat. Stir in the additional fat (either more butter or coconut oil) and cinnamon. This last addition is like putting on the finishing touch of a masterpiece.
Pour the pudding into individual serving dishes or a large bowl. Cover with plastic wrap (make sure it touches the surface to prevent a skin from forming), and refrigerate for at least 4 hours, or overnight if you can resist.