How to Make It
Combine cream, milk, sugar, and salt in a saucepan over medium. Bring to a boil, and cook, stirring often, until sugar is dissolved, about 3 minutes. Remove from heat.
Whisk together egg yolks in a medium bowl. Gradually whisk about one-fourth of hot cream mixture into yolks, whisking constantly. Gradually whisk yolk mixture into remaining cream mixture in saucepan. Cook over medium-low, stirring often, until mixture coats a spoon and a thermometer registers 170°F.
Remove mixture from heat, and pour through a fine wire-mesh strainer into a bowl. Cover and refrigerate until well chilled, about 4 hours.
Uncover, and whisk in mayonnaise until smooth. Pour mixture into an ice cream maker; freeze according to manufacturer’s instructions. Transfer to a freezer-safe container; cover and freeze until firm, at least 2 hours.