Line a second 8x8 inch (20x20 cm) pan with parchment paper so that there's an overhang around the edges. I recommend lightly greasing the pan first so that the parchment paper stays in place. If you don't have a second pan, remove the Nutella (still attached to the parchment) from the pan in the freezer. Place the Nutella back in the freezer and line the original pan again.
Add about 2/3 to 3/4 of the pumpkin dough into your prepared pan. Spread into an even layer. Pop the pan into the oven to bake for about 18-20 minutes, or until the top is set.
Remove form the oven (keep the oven turned on). Let the base layer cool for about 5-10 minutes.
Remove the frozen Nutella from the freezer. Peel off the parchment paper, then place the frozen Nutella on top of the pumpkin blondie base.
Lightly grease your hands. Then spoon/pinch off sections of the remaining pumpkin dough. Flatten them down into disc shapes. Place the discs on top of the Nutella layer, working to cover the Nutella layer with pumpkin dough. If you are not able to cover all of the Nutella - that is totally OK.
Place the pan back in the oven. Bake for an additional 15-20 minutes, or until the sections on the top look set. Bake time will depend on your oven and how gooey you like your pumpkin blondie layers. I baked my base layer for 18 minutes and then the whole pan for an additional 18 minutes and my bars were still on the gooier side.
Cool the bars in the pan until the pan is no longer warm to the touch.
When ready to slice, lift the bars out of the pan using the overhang of the parchment. Place on a cutting board, peel back the parchment and slice using a sharp knife.