Step 1

In a medium saucepan over medium heat, warm the cream, milk and 1 cup of the dulce de leche, stirring constantly until the mixture is blended and steam begins to rise from the surface, about 4-5 minutes.

Step 2

In a large heatproof or metal mixing bowl, whisk together the egg yolks, sugar (if using), vanilla, and salt until blended.

Step 3

Slowly add the hot cream mixture, whisking constantly until fully incorporated.

Step 4

Transfer the mixture back to the saucepan and set over medium-low heat. Cook without allowing to boil, stirring slowly and continuously with a wooden spoon or spatula, until the mixture thickens to a custard-like consistency, 6-10 minutes, depending on your stove.

Step 5

Set a fine-mesh sieve over a clean bowl and pour the custard mixture through. Set the bowl in a larger one filled halfway with ice and water and cool the custard to room temperature, stirring occasionally. Refrigerate 1+ hours until chilled.

Step 6

Transfer the custard mixture to an ice cream maker or Kitchenaid mixer attachment and churn according to the manufacturer's instructions. At the end of the freezing stage, add the remaining ½ cup dulce de leche into the churning ice cream until it is swirled throughout.

Step 7

Transfer the ice cream to a freezable container with a lid (like a loaf pan), cover and freeze until firm, 3 to 4 hours.