Prep the crust: If using a store-bought crust, fit it into a 9-inch pie plate and crimp the edges.
If making a graham crust, mix crumbs, sugar, salt, and melted butter until it resembles damp sand. Press firmly into the bottom and up the sides of the pie plate. Chill while you make the filling.
Heat the oven: Preheat to 350°F (175°C).
Place a rack in the lower-middle position to help the bottom crust crisp.
Whisk the dry mix: In a large bowl, whisk sugar, cornstarch, salt, cinnamon, cardamom, ginger, cloves, and black pepper until evenly combined. This prevents spice clumps later.
Build the custard: Add eggs and whisk until smooth and slightly thick. Pour in milk, cream, and vanilla.
If using, whisk in instant tea powder or the cooled, reduced black tea. The mixture should be silky with specks of spice.
Fill the crust: Pour the custard into the prepared crust. Tap the pie plate gently on the counter to release air bubbles.
Bake: Bake for 35–45 minutes.
The edges should be set and the center should have a slight wobble. If the crust browns too quickly, tent the edges with foil.
Cool fully: Set the pie on a rack and cool to room temperature, about 2 hours. Then chill for at least 3 hours, or overnight, to finish setting.
Serve: Slice with a sharp knife.
Wipe the blade between cuts for clean slices. Top with whipped cream and a dusting of cinnamon.