Direction :

1. Combine cream and milk in bowl or pitcher, set aside. Whisk egg yolks and cornstarch (read note in next sentence first) in medium bowl, set aside. Note: There has to be a better way to whisk egg yolks and cornstarch than what I have been doing, which causes the yolks to clump all around the whisk. This is what I’ll do next time: Crack yolks into bowl. Spoon a little bit of the cornstarch into the yolks. Stir with a spoon until incorporated, then add more cornstarch and continue this process until all of the cornstarch has been added.
2. Combine brown sugar, kosher salt and 1/4 cup water in pot. Place over medium-high heat and let sit until edges start to brown. Tilt pot as needed to even the browning until caramelized, nutty and deep brown, about 10 minutes. Notes: The mixture should be bubbling (not crazily, however) the whole time, so adjust heat as necessary. Do set a timer. It’s hard to tell visually when the mixture is ready, but every time that I’ve made this, 10 minutes seemed to be the magic number.
3. Immediately whisk in cream mixture, mixture will steam and caramel will seize. Bring to a boil, then reduce heat to medium. Whisk a cup at a time into egg mixture until half is incorporated. Remove from heat, and immediately whisk egg mixture back into pot until custard is very thick, about 2 minutes.
4. Whisk in rum. Pass through a fine mesh strainer. Transfer to a storage container (preferably glass or pyrex). Cover with plastic wrap, allow to cool, and refrigerate until completely chilled, the longer the better.
5. Transfer mixture to ice cream maker and freeze according to your machine’s instructions. Freeze until ready to serve.