Add the whole milk, heavy cream, maple syrup, salt, star anise and half of the granulated sugar to a medium saucepan.
In a small bowl, combine the cinnamon, ginger, cardamom, cloves and nutmeg. Whisk the ground spices into the dairy mixture.
Warm over medium-low heat until steaming and small bubbles begin appearing around the edges. Do not let it boil.
Remove the saucepan from the heat, cover and let the spices steep for 5 minutes.
Meanwhile, whisk the egg yolks with the remaining sugar until smooth and slightly lightened.
Remove the star anise from the cream mixture.
Slowly pour approximately 1 cup of the warm cream mixture into the egg yolks while whisking constantly.
Pour the tempered egg mixture back into the saucepan.
Cook over medium-low heat, stirring continuously with a silicone spatula, until the custard reaches 170–175°F and lightly coats the back of the spatula.
Remove the custard from the heat and stir in the vanilla extract.
Pour the custard through a fine-mesh strainer to catch any pieces of cooked egg. Whisk the fine chai spices collected by the strainer back into the custard—we want those visible spice specks.
Place the custard over an ice bath and stir until cooled. Cover and refrigerate for at least 4 hours, preferably overnight.