In a bowl, combine the heavy cream, milk, lemongrass, sliced ginger, and 2 sliced limes. Allow this to sit in the refrigerator for at least an hour.
Pour the contents from the bowl into a saucepan. Add the vanilla bean, sugar, and salt. Heat over medium-high heat and stir to combine together. Bring to a boil. Reduce the heat and heat for 20 minutes. Make sure to stir so the dairy does not stick to the bottom of the pan.
In a bowl, combine the egg yolks, lime zest, lime juice, and shredded ginger. Mix until everything is combined.
Once the mixture in the saucepan has been heated for 20 minutes as previously instructed, remove it from the heat. Remove the large chunks, such as the sliced lime, from the cream mixture. Slowly introduce the hot mixture into the egg yolk mixture. You want to do this slowly (about a half cup at a time) and to be continuously whisking to avoid cooking the eggs too quickly.
Once you’ve added ¾ of the hot mixture into the bowl, return to the saucepan. Warm the mixture up. While the mixture is cooking a second time, scrape the seeds from the vanilla bean and add them. Heat until the cream mixture has reached a temperature of 180°F.
Pour the ice cream base into a bowl. Cover and refrigerate for at least one hour (overnight is best).
Follow the instructions of your ice cream maker to finish up the ice cream. Place in a freezer-safe container and let it freeze overnight. When you want to serve the ice cream, remove it from the freezer 10 minutes before scooping for an easier scoop.
