Place kernels in an air popper. In a large bowl, make popcorn according to manufacturer's instructions. Toss in melted butter. Set aside.
Pour the cream and milk into a saucepan and add vanilla beans and seeds. Place over low heat and cook for 8 minutes. Remove from the heat just before it comes to a boil, pour over the popcorn and stir well. Cover the bowl with plastic wrap, set aside to cool, and leave in the fridge to infuse overnight.
The next day, bring the mixture back to room temperature and strain it through a fine mesh sieve into a seperate bowl, squeezing all the flavour out of the popcorn into the milk before discarding the popcorn and vanilla pod.
Place the egg yolks in a large bowl with 1/2 cup of white sugar. Whisk until light and fluffy, then use a ladle to spoon the cream mixture into the eggs, continuously whisking as you pour. Return the custard to a large saucepan with 1/4 tsp of salt. Place over medium heat and cook for 5-7 minutes, stirring continuously with a rubber spatula, until the mixture is thick enough to coat the spatula and leaves a gap when you draw a line through it with your finger.
Remove from the heat and transfer to a bowl to cool. Store in the fridge until well chilled. Pour the custard into an ice cream machine and churn for 35 minutes, until semi frozen.
Transfer to a plastic container and top with 1/2 cup of caramel popcorn then drizzle with 2 tbsp of caramel sauce. Store in the freezer, covered, for at least 6 hours or until firm and scoopable.
To serve, divide the ice cream among bowls and serve with remaining caramel popcorn and caramel sauce.