Whisk the egg yolks, dark brown sugar, salt, and molasses in a medium, heat resistant bowl, and set aside.
Melt the butter in a saucepan over medium heat and continue to cook until the solids turn a dark, rich brown. Watch it carefully so it doesn't burn!
Slowly pour the brown butter over the egg yolk mixture, whisking to combine.
In the same saucepan you used to brown the butter, heat the cream and just 1 cup of the milk (reserve the rest of the milk), until just about to boil. It should be starting to bubble around the edges.
Pour a small amount of the hot cream mixture into your egg yolk mixture and whisk to temper the eggs.
Pour the egg yolk mixture back into the saucepan with the cream mixture, whisking constantly as you pour.
Cook over medium heat, whisking frequently, until it has thickened a bit and will coat the back of a spoon.
Pour the cooked custard over the remaining cup of milk, through a strainer if you’d like to filter out any small bits of cooked egg.
Add the vanilla extract, and whiskey, and stir to combine.
Cool the mixture completely, preferably overnight.
Process in an ice cream maker according to the manufacturer’s instructions. Add your finely chopped chocolate to the ice cream machine when the ice cream is almost done. You want it to mix in evenly, so add it in about a minute or so before you stop the machine.
Pour your finished ice cream in a freezer safe container, top with more chopped chocolate if you'd like, and enjoy! It will be best eaten within a day or two of making.