Preheat oven to 350°F (175°C). Line a 9×13 inch baking pan with parchment paper.
In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla extract and pumpkin puree.
In a separate bowl, whisk together the flour, chai spice blend, pumpkin pie spice, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.
Pour the batter into the prepared baking pan and spread evenly.
Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Let the bars cool completely in the pan before lifting them out using the parchment paper.
While the bars are cooling, prepare the glaze by whisking together the powdered sugar and milk (or cream) until smooth. Add more milk as needed to reach the desired consistency.
Drizzle the glaze over the cooled bars. Cut into squares and serve.
