Prepare the Crust: In a food processor, combine all-purpose flour, sugar, and salt; pulse until blended. Cut in cold unsalted butter until sandy. Gradually drizzle in cold water while pulsing until dough holds. Shape into a disk, wrap, and chill for 30 minutes.

Roll Out the Crust: Flour work surface and roll dough into a 12-inch circle, about ⅛ inch thick. Place in a tart pan, trim excess. Freeze for 10 minutes, preheat oven to 375°F (190°C). Blind bake for 15-18 minutes until golden.

Make the Chai Custard: In a saucepan, combine whole milk, heavy cream, and black tea bags; simmer for 10 minutes, remove tea bags. Whisk egg yolks, sugar, cornstarch, vanilla extract, and chai spice until smooth.

Temper the Egg Mixture: Gradually whisk warm milk mixture into egg mixture, stirring constantly. Return to saucepan; cook over medium heat, stirring until thickened (about 4 minutes). Cool for 10 minutes before pouring into tart shell.

Assemble with Pears: Thinly slice pears and arrange atop custard in concentric circles. Press slices gently. Bake at 350°F (175°C) for 20-25 minutes until custard jiggles slightly.

Cool and Serve: Remove from oven and cool for at least 1 hour. Optionally refrigerate. Dust with powdered sugar before serving, pair with honey or whipped cream.