In a medium, heavy-bottomed saucepan over medium-high heat, pour 2¼ cups (563 ml) of milk; bring to a simmer.
Meanwhile, in a medium bowl, whisk together the Redpath® Dark Brown Sugar, cornstarch, and salt until well combined and no lumps remain. Whisk in the remaining ¼ cup (63 ml) milk and the lightly beaten eggs until smooth (see Chef’s Tips).
Once the milk begins to simmer, remove from heat. Slowly pour the hot milk into the brown sugar-egg mixture while whisking constantly to temper the eggs; this prevents the eggs from scrambling.
Place a fine mesh sieve over a medium bowl. Set aside.
Rinse the saucepan used to simmer the milk (no need to dry), pour in the mixture, and place over medium to medium-high heat. Whisk constantly until the custard begins to thicken. Switch to a heatproof spatula to ensure pudding does not adhere to the bottom or sides of the saucepan. Switch back to the whisk to incorporate the lumps back into the pudding. Continue to cook and whisk/stir until the pudding begins to bubble. Cook for another minute, remove from heat, and immediately pour the pudding through the sieve. The sieve will catch any cooked egg or lumps from the pudding; discard.
Immediately and vigorously whisk in the cubed butter, vanilla extract, and whisky (if using) into the hot pudding until completely smooth and fully incorporated.
Portion into glasses or bowls. Serve warm or place into the fridge to chill thoroughly; at least 3 hours.
Garnish with whipped cream and other toppings if desired.