Heat cream and 1 cup of the milk in a heavy sauce pan over medium heat until just scalded.
Add the popped popcorn to the pan and let steep for one hour.
Strain the popcorn milk through a fine mesh sieve into a large liquid measuring cup.
Add enough of the remaining milk to make 3 cups total (about one more cup, give or take)
Return the milk to the sauce pan and return heat to medium.
Separate your eggs and beat the egg yolks, sugar, and salt in a separate bowl with an electric mixer on high speed until light and fluffy, about 2 minutes.
When milk is hot but not scalded, add a cup to the egg mixture and whisk vigorously.
Pour the tempered (warmed) eggs back into the sauce pan with the remaining milk.
Reduce heat to low/medium-low.
Cook, whisking constantly, until the custard reaches 185Â°F (give or take a Fahrenheit) on an instant-read thermometer and is thick enough to just coat the back of the spoon.
Remove pan from the burner, stir in vanilla extract, and continue stirring for another minute or so to release some of the heat.
Strain the cooked custard through a fine-mesh sieve, if desired.
Chill the mixture in the refrigerator until completely cool, stirring occasionally, about 2 hours
Put in the ice cream maker of your choice and follow the manufacturers directions.