In a large bowl, whisk the cake flour, 3 1/2 teaspoons of chai spice mix, the baking powder, baking soda, and salt together. Set aside.
1 3/4 cups cake flour, 3/4 tsp baking powder, 1/4 tsp baking soda, 1/4 tsp salt
Using a hand mixer, beat the butter and sugar together on high speed until smooth and creamed, about 2 minutes. Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed.
1/2 cup unsalted butter, 1 cup granulated sugar
Beat in the egg whites on high speed until combined, about 2 minutes. Beat in the sour cream and vanilla extract. Scrape down the sides and up the bottom of the bowl as needed.
3 large egg whites, 2 tsp vanilla extract, 1/2 cup sour cream
With the mixer on low speed, add the dry ingredients until just incorporated. With the mixer still running on low, slowly pour and mix in the chai milk just until combined.
Scoop/spoon the batter into the liners. Fill only 2/3 full to avoid baking over the sides. Bake for 20-22 minutes, or until a toothpick inserted in the center comes out clean. Allow the cupcakes to fully cool before frosting.