Preheat oven to 350°F (175°C). Grease and line an 8×8-inch baking pan with parchment paper.

In a medium bowl, whisk together flour, baking powder, salt, cinnamon, ginger, and cardamom.

In a large bowl, beat together butter and brown sugar until creamy.

Add the eggs, one at a time, beating well after each addition. Stir in vanilla extract, brewed coffee, milk, and chai tea concentrate.

Gradually fold in the dry ingredients, mixing until smooth and well combined.

Pour the batter into the prepared pan and smooth the top.

Bake for 25–30 minutes, or until a toothpick inserted in the center comes out clean. Let cool in the pan.

For the icing: Whisk together powdered sugar, chai concentrate, cinnamon, and vanilla extract until smooth.

Drizzle the icing over the cooled bars. Let set for 15 minutes before slicing into squares.