Preheat oven to 350°F. Spray a 10 x 15-inch baking pan with nonstick cooking spray and line it with parchment paper.
In a large bowl, add pumpkin, sugar, oil, orange juice, eggs, and vanilla extract. Stir until well blended.
In a medium bowl, whisk together flour, baking powder, baking soda, kosher salt, cinnamon, nutmeg, ginger, and cloves. Gradually add the dry mixture to the pumpkin mixture, stirring until just combined.
Pour the batter into the prepared pan, spreading it out evenly.
Bake for 25-30 minutes, or until the bars are set and a toothpick inserted into the center comes out with a few crumbs, but not wet batter.
Allow the bars to cool completely in the pan.
In the bowl of a stand mixer fitted with the paddle attachment, mix cream cheese, butter, milk, and vanilla extract for 1-2 minutes on medium speed.
Add confectioners’ sugar, one cup at a time, until the frosting is light and creamy.
Spread the frosting on top of the cooled bars and top with crushed walnuts.
Cut and serve. Enjoy!