Whisk the flour, baking powder, baking soda, cream of tartar, and salt together until combined. Set aside.

In a large bowl using a handheld or stand mixer fitted with a paddle attachment, beat the butter, granulated sugar, and brown sugar together on high speed until completely smooth and creamy, about 2 minutes. Beat in the eggs and vanilla extract on high speed. Scrape down the sides and bottom of the bowl as needed.

On low speed, slowly mix the dry ingredients into the wet ingredients until combined. Beat in the white chocolate chips. The cookie dough will be thick. Cover dough tightly with aluminum foil or plastic wrap and chill for 1 hour and up to 3 days.

Remove cookie dough from the refrigerator. If the cookie dough chilled longer than 3-4 hours, let it sit at room temperature for about 20 minutes. This makes the cookie dough easier to scoop and roll.

Preheat oven to 350°F (177°C). Line two large baking sheets with parchment paper or silicone baking mats. (Always recommended for cookies.) Set aside.

Combine the topping ingredients. Set aside.

Roll cookie dough into balls, about 1.5 Tablespoons of dough per cookie. (I use a medium cookie scoop.) Roll each in the topping mixture and arrange 3 inches apart on the baking sheets. Bake for 11-13 minutes or until lightly browned on the sides. The centers will look very soft.

Remove from the oven and allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely. While the cookies are still warm, I like to press a few more white chocolate chips into the tops—this is only for looks!