1-First, whisk together the 3 cups all-purpose flour, 1 teaspoon baking powder, 1/2 teaspoon baking soda, 1 teaspoon cream of tartar, and 1/2 teaspoon salt until combined, then set aside. Next, beat the 1 cup unsalted butter, 1 cup granulated sugar, and 1/2 cup packed light brown sugar on high speed until smooth and creamy, about 2 minutes. Add the 2 large eggs and 2 teaspoons pure vanilla extract, and beat until well combined.

2-Slowly mix the dry ingredients into the wet ingredients on low speed until combined, then stir in the 1 1/2 cups white chocolate chips. Cover the dough and chill it for 1 hour to up to 3 days for better texture. If the dough has chilled longer than 3-4 hours, let it sit at room temperature for 20 minutes before scooping. Preheat the oven to 350°F (177°C) and line baking sheets with parchment paper or silicone mats.

3-Forming and Baking the Cookies: Combine the topping ingredients: 1/2 cup granulated sugar, 1 1/2 teaspoons ground cinnamon, 1 teaspoon ground ginger, 1 teaspoon ground cardamom, and 1/2 teaspoon ground allspice, then set aside. Roll the dough into balls of about 1.5 tablespoons each, roll them in the chai spice sugar topping, and space them 3 inches apart on the baking sheets. Bake for 11-13 minutes until lightly browned on the edges; the centers will be very soft.

4-After baking, cool the cookies on the baking sheet for 5 minutes before transferring to a wire rack. While warm, you can press extra white chocolate chips on top for a nice look. This step-by-step approach, including the chilling time, ensures the cookies have that perfect chewy center and crispy edge. Total time is about 1 hour 30 minutes, with active prep around 20 minutes and baking about 12 minutes per batch.