Preheat your oven to 350°F (175°C) and line a cupcake tin with liners. Spray liners lightly with cooking spray.

In a small bowl, blend together the chai spices: cinnamon, ginger, cardamom, nutmeg, allspice, cloves, and black pepper.

In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, three teaspoons of chai spice mix, and salt. Set aside.

In a separate bowl, whisk the milk and sourdough discard until smooth. Set aside.

Beat together the granulated sugar and unsalted butter until light and fluffy, about 4-5 minutes.

Add the eggs one at a time, mixing until fully incorporated. Pour in the sour cream and vanilla extract, blending until smooth.

Gently alternate adding the dry flour mixture and the wet milk mixture to the batter, starting with the dry ingredients.

Divide the batter evenly among the prepared cupcake liners, filling each about 3/4 full.

Bake for 16-17 minutes, checking for doneness with a toothpick.

Let them cool in the tin for about 5 minutes, then transfer to a wire rack to cool completely.

Beat room-temperature butter and powdered sugar together until smooth and creamy.

Add the chai spice mix, vanilla, and a pinch of salt, combining until flavors meld.

Slowly incorporate heavy cream until desired consistency is reached.

Frost each cooled cupcake generously with the chai-spiced buttercream.