Using a sharp knife, chop Heath Bars into pieces measuring about 1/2 inch.
Place candy pieces in a covered bowl and freeze until needed.
Pour 1 cup heavy cream and whole milk into a medium saucepan.
Place saucepan over medium-low heat and cook until the mixture is steaming but not boiling.
Whisk eggs, sugar and salt in a heat-safe mixing bowl until smooth and slightly lightened.
Slowly pour about 1 cup of the hot cream mixture into the eggs, whisking constantly.
Pour the tempered egg mixture back into the saucepan.
Cook over medium-low heat, stirring constantly, until the custard reaches 170°F and lightly coats the back of a spoon.
Do not allow the custard to boil.
Remove saucepan from heat.
Stir in the remaining 1 cup heavy cream and vanilla.
Pour custard through a fine-mesh strainer into a clean bowl.
Cover and refrigerate for at least 4 hours or until thoroughly chilled.
Pour chilled custard into an ice cream maker.
Freeze according to the manufacturer’s instructions.
Add frozen Heath Bar pieces during the final 2 minutes of churning.
Transfer ice cream to a freezer-safe container.
Press parchment paper or plastic wrap directly against the surface.
Cover and freeze for at least 2 hours before serving.
Allow ice cream to stand at room temperature for about 5 minutes before scooping.