Preheat the oven to 350 degrees
In a large bowl, add the cake mix, vegetable oil, eggs, sour cream, canned pumpkin, and pumpkin pie spice. Using a hand mixer, blend everything together until it’s evenly combined.
In a small sized bowl, stir together the brown sugar and chopped walnuts.
Pour half of the pumpkin cake mixture into a sprayed 9 x 13” pan.
Evenly sprinkle the walnut and brown sugar mixture onto the top.
Add the rest of the pumpkin cake batter to the top and spread it out evenly.
Bake the cake for about 35-40 minutes or until it’s cooked all the way through.
Once the cake is done, whisk together the powdered sugar, milk and vanilla to prepare the glaze and pour the glaze evenly over the cake and place it into to fridge to cool completely.
Finally, cut it into squares, serve and enjoy!