In a medium heavy pot cook the sugar over medium high heat until it starts to turn golden brown and melts. After about 3 minutes, add the butter, milk and cream. Reduce the heat to medium and cook until everything is melted and is barely simmering. Remove from heat and set aside. In another small bowl whisk together the egg yolks, vanilla and salt. Whisk constantly until the mixture turns to a light yellow color and becomes thick. Slowly add about ¾ cups of the warm cream into the egg mixture and stir until smooth. Then add the rest of the cream mixture and continue to stir. Transfer the entire mixture back into the pot and stir until it thickens, but be careful not to let it boil.

Once thick, remove from the heat and transfer to a clean bowl. Cover the mixture with plastic wrap and refrigerate for at least 4 hours. Pour the custard mixture into your ice cream machine and mix according to the manufacturers instructions. After the mixer is done, transfer the ice cream into a container and freeze for at least 2 hours before eating.