Step 1Cook the mandarin juice over medium heat until it is about 1 cup. The juice will darken in color and take on a light syrup consistency. Be careful because the juice will scorch as it gets closer to the right consistency; pouring it into a smaller pot will help reduce the risk of scorching. When the juice is the right consistency, strain it into a separate container and cool completely.
Step 2Heat the milk, cream, vanilla bean and half of the sugar, but do not bring fully to a boil.
Step 3Beat the egg yolks and the rest of the sugar until pale yellow.
Step 4Remove the vanilla bean from the liquid and scrape a few seeds back into the mixture.
Step 5Gradually whisk 1/3 of the hot liquid into the egg yolks to temper them. Whisking constantly, add the tempered mixture back into the milk/cream mixture. Cook the mixture over a medium-low flame, stirring constantly with a wooden spoon to keep it from scorching.
Step 6When the mixture is thick enough to coat the back of a wooden spoon, it is the right consistency. Strain it into a bowl and cool it over an ice bath.
Step 7Add the reduced mandarin juice to the cooled ice cream base and freeze it in an ice cream maker according to the manufacturer's instructions.