Melt unsalted butter in a light-colored saucepan over medium heat. Swirl occasionally as it foams and crackles. After 5-7 minutes, toasted golden-brown milk solids will settle at the bottom with a fragrant nutty aroma. Immediately pour into a mixing bowl to cool for 15 minutes.

Preheat your oven to 350°F (175°C) and line two large baking sheets with parchment paper. In a small shallow bowl, whisk together the rolling sugar and all chai spices (cinnamon, cardamom, ginger, cloves, and nutmeg) until well blended.

Whisk the brown sugar and granulated sugar into the warm browned butter until glossy. Whisk in the egg, egg yolk, and vanilla extract until smooth and slightly thickened.

In a separate bowl, whisk together the flour, cream of tartar, baking soda, and sea salt. Fold the dry ingredients into the butter mixture with a rubber spatula just until no flour pockets remain. Do not overmix.

Scoop 2-tablespoon portions of dough, roll into smooth balls, and generously roll each ball in the sparkling chai spice sugar to coat completely. Place 2 inches apart on prepared sheets.

Bake at 350°F (175°C) for 9 to 11 minutes until the edges are set and crackly but the centers remain soft and puffed. Bang the pan gently on the counter right out of the oven to create gorgeous ripples, cool for 10 minutes on the sheet, and enjoy!