Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a large mixing bowl, beat softened butter and granulated sugar with an electric mixer until the mixture is light and fluffy, about 2-3 minutes. Observe the color brighten and volume increase.
1 cup unsalted butter
Add the egg and vanilla extract to the bowl and beat until fully incorporated, about 1 minute. Look for a smooth, homogeneous batter.
1 cup unsalted butter
In a separate bowl, whisk together flour, baking soda, salt, cinnamon, and cardamom. Pour the dry ingredients into the wet mixture gradually, mixing on low until just combined.
1 cup unsalted butter
Fold in the chopped chai leaves and cold brew coffee using a silicone spatula, distributing evenly. The dough will appear slightly speckled and moist.
1 cup unsalted butter
Using a spoon or cookie scoop, portion the dough onto the prepared baking sheet, spacing cookies about 2 inches apart. Flatten each slightly with the back of the spoon.
Bake in the preheated oven for 10-12 minutes, or until the cookies turn golden around the edges and the centers look set. The aroma of spices and coffee should be noticeable.
Remove the cookies from the oven and allow them to cool on the baking sheet for 5 minutes. Transfer to a wire rack to cool completely before serving.