Bring the brown sugar and water to a boil in a large saucepan over medium heat, stirring until the sugar is dissolved.
Boil for 2 minutes, stirring constantly.
Add the cream and 1 and 1/2 cups (375 ml) of milk and bring to a boil, stirring.

Mix the cornstarch, salt, sugar, and egg yolks, then dilute with the remaining milk.

Pour the preparation into the hot milk and mix well with a whisk until thickened.
Add the butter and Scotch whisky and mix.

Pour into cups, cover with plastic wrap and refrigerate for at least 4 hours.