Preheat your oven to 350°F/175°C. Grease a 10 x 15 inch baking pan, or line it with parchment paper, you'll want to have enough paper over the edges so you can easily remove the bars after cooking.
In a large bowl, whisk flour, baking powder, baking soda, pumpkin pie spice, and cinnamon, then set aside.
2 cups all-purpose flour, 1 teaspoon baking powder, 1 teaspoon baking soda, 1 teaspoon Pumpkin Pie Spice, 1½ teaspoons cinnamon
In a separate bowl, whisk eggs, oil, brown and granulated sugar, pumpkin puree, milk, and vanilla extract until fully combined and smooth. Then, pour the mixture into the dry ingredients and use either a mixer or a whisk until combined, the batter will be thick.
3 large eggs, ⅔ cup vegetable oil, 1 cup brown sugar, ¼ cup granulated sugar, 15 ounces pumpkin puree, ¼ cup whole milk, 2 teaspoons vanilla extract
Pour the batter into your prepared baking pan and spread it into an even layer. Bake until the center springs back when it's gently pressed, approximately 25 - 30 minutes. Remove from the oven and place your pan on a wire rack to cool completely.
In a large mixing bowl, beat unsalted butter and cream cheese until smooth, then add confectioner's sugar and vanilla extract, and, using an electric mixer, mix until creamy and smooth. Tip: Place the cheese frosting in the fridge for 30 minutes so it 'sets' a little and is easier to use and cut; however, you don't have to do this.
½ cup unsalted butter, 8 ounces cream cheese, 3 cups confectioners sugar, 1 teaspoon vanilla extract
When the base has cooled completely, carefully remove it from the pan, spread the cream cheese frosting evenly over the top, and dust lightly with cinnamon and any preferred sprinkles. Cut into even bars, serve, and enjoy!
Sprinkles