In a large bowl, whisk together flour, sugar, and salt. Add the cold cubed butter and use a pastry cutter or your fingertips to work it into the flour until the mixture resembles coarse crumbs with some pea-sized butter pieces remaining.
Drizzle in ice water, 1 tablespoon at a time, and mix until the dough just comes together. Form into two discs, wrap in plastic, and refrigerate for at least 30 minutes.
While the dough chills, mix all the chai spice ingredients in a small bowl.
Peel, core, and slice the apples to about ¼-inch thickness. In a large bowl, gently toss the sliced apples with sugar, cornstarch, lemon juice, vanilla, salt, and your chai spice blend until every slice is evenly coated.
Preheat your oven to 425°F (220°C) and place a baking sheet on the lower rack.
Roll out one disc of dough on a floured surface to a 12-inch circle. Transfer to a 9-inch pie dish, allowing the edges to hang over slightly.
Pour in the apple filling, mounding slightly in the center, and dot with butter pieces if using.
Roll out the second disc and either place it whole over the filling or create a lattice pattern. Trim excess dough, leaving a 1-inch overhang. Fold the edges under and crimp decoratively.
Brush the top crust with egg wash and sprinkle with turbinado sugar.
Place the pie on the preheated baking sheet and bake at 425°F for 20 minutes. Reduce temperature to 375°F (190°C) and continue baking for 30-35 minutes until the crust is golden brown and the filling is bubbling. If the edges brown too quickly, shield them with foil.
Allow your Chai Spice Apple Pie to cool on a wire rack for at least 2 hours before slicing.