In a large saucepan, combine the milk and cream, and bring to a simmer over medium heat and immediately turn off the heat and set aside.
In a large skillet, melt the butter over medium-high heat. Stir in the Light brown sugar and cook 5 to 7 minutes, stirring constantly, to caramelize the mixture. (You will smell caramel signaling that the mixture is ready.)
Whisking constantly, gradually add the butter/brown sugar mixture to the hot milk/cream mixture. If the mixture is not smooth, blend for 20 seconds.
Put the egg yolks in a medium bowl. Whisk in about 1/2 cup of the hot milk mixture. Whisk in the cornstarch and salt until dissolved. Whisk the cornstarch mixture back into the hot milk mixture in the saucepan.
Add the scotch.
Whisking constantly, cook over medium-high heat until thick and just boiling and you see a few large bubbles boiling up to the top.
Turn off the heat and whisk in the vanilla extract.
Pour into the pre-baked pie shell and chill.
Preheat oven to 400 degrees F.
Meringue top: Whip whites with the salt to soft peaks, then add sugar and whip until sugar is dissolved and whites are glossy. Spread meringue on top of the slightly cooled pie.
Bake for 5 minutes until lightly cappuccino color. Chill until ready to serve.