Infuse the Milk and Cream with Spices: In a medium-sized, heavy-bottomed saucepan, combine the whole milk and heavy cream. Add the cinnamon stick, star anise, crushed cardamom pods, cloves, allspice, peppercorns, and fresh ginger slices. Warm the mixture over medium-low heat just until it’s hot but not boiling (about 5–10 minutes). Remove the pan from heat, cover loosely, and allow the spices to steep for 45 minutes, infusing the dairy with their warm, aromatic flavors.
Brew the Tea and Sweeten the Base: After the steeping period, add the black tea bags and half of the sugar to the spiced milk mixture. Gently warm the liquid again for a couple of minutes without bringing it to a simmer. Remove from heat and let the tea steep for 10 minutes, allowing the color and flavor to deepen. Taste the mixture and, if desired, sprinkle in the optional masala chai spice to enhance the chai flavor.
Prepare the Egg Yolk and Sugar Mixture: While the tea is steeping, whisk together the egg yolks and the remaining sugar in a clean bowl. Whisk continuously until the mixture becomes pale and slightly glossy, which helps incorporate air and dissolve the sugar for a creamy custard texture.
Temper the Eggs to Prevent Curdling: Slowly pour about two tablespoons of the warm milk-tea mixture into the egg yolks while whisking vigorously to gently raise the temperature of the eggs. Repeat this step gradually, adding the warm liquid in small amounts until the eggs are warmed through. This tempering process prevents the eggs from cooking too quickly and scrambling.
Cook the Custard to Thicken: Remove the tea bags from the milk mixture. Pour the tempered egg mixture back into the saucepan. Return the pan to medium-low heat and stir constantly with a wooden spoon or spatula. Warm the custard carefully until it thickens slightly and coats the back of the spoon, reaching about 170°F (76°C). Do not let it boil, as overheating will cause curdling. Remove from heat once thickened.
Strain and Chill the Custard: Pour the custard through a fine mesh strainer into a clean bowl to remove all the whole spices and any cooked egg bits, ensuring a smooth base. Let the strained custard cool to room temperature, then cover and refrigerate for at least 4 hours, preferably overnight, until thoroughly chilled.
Churn the Ice Cream: Following your ice cream maker’s instructions, churn the cold custard until it reaches a soft-serve consistency. During the last few minutes of churning, fold in chopped crystallized ginger pieces for an extra burst of sweet spice, if using.
Freeze to Firm Up: Transfer the churned ice cream into an airtight container and freeze for several hours until firm enough to scoop. Serve chilled and enjoy the creamy, spiced delight!