Preheat the oven to 350°F. Line an 8×8-inch baking pan with parchment paper and lightly spray with nonstick cooking spray.
Press the Pillsbury Chocolate Chip Cookie Dough evenly into the bottom of the prepared pan.
Spread the Nutella evenly over the cookie dough, leaving a small border around the edges.
Flatten pieces of the Nestlé Toll House Trick or Treats Chocolate Cookie Dough between your hands and arrange them over the Nutella. Gently press the pieces together to create an even top layer.
Decorate the top with Halloween sprinkles and royal icing pumpkins, gently pressing the pumpkins into the dough.
Bake for 30–38 minutes, or until the top is set and the edges are golden. Since the bars are thick, the center will stay soft while warm and continue to set as the bars cool.
As soon as the bars come out of the oven, gently press the Reese’s Mini Pumpkins into the top.
Let the bars cool completely before lifting them from the pan and cutting into squares.