In a medium saucepan, bring the cream, milk, brown sugar and salt to a simmer over medium heat, about 8 minutes, whisking to dissolve the sugar. Remove from the heat, whisk in the scotch and vanilla and set aside to cool slightly.
In a medium bowl, whisk the egg yolks and cornstarch until combined. Whisk in 1/4 cup of the cream mixture until smooth, adding slowly so you don't scramble the eggs. Whisk in another 1/4 cup cream mixture until combined, then slowly pour the entire egg mixture into the saucepan, whisking to combine. Bring to a simmer over medium-low heat, stirring constantly with a wooden spoon until thick, about 5 minutes. Remove from the heat and stir in the butter until melted and smooth.
Strain the pudding through a fine-mesh sieve into a medium bowl or individual cups. Gently press plastic wrap on the surface of the pudding to prevent a skin from forming. Refrigerate for at least 6 hours or overnight. Top with the toffee candy.