Preheat oven to 425 F (218 C) and prepare a 12 count muffin pan. Grease well with cooking spray or line with muffin liners. Since this recipe yields about 15 muffins, you can either prepare a second muffin pan, or bake the muffins in 2 batches if you have only one muffin pan.
In a large bowl, combine the dry ingredients: all purpose flour, baking soda, ground cinnamon, pumpkin pie spice, and salt. Whisk lightly and set aside.
In a separate medium sized bowl, combine the wet ingredients: oil, granulated sugar, brown sugar, pumpkin puree, eggs and milk. Whisk until combined.
Pour the wet ingredients into the dry ingredients and whisk until you can no longer see the flour and all the ingredients are combined.
Using a spoon or an ice cream scoop, fill each liner with batter until almost full.
Drop little spoonfuls of Nutella in the centre of each muffin (about 1 teaspoon each). Using a toothpick, gently swirl Nutella in any pattern you like. Just make sure not to swirl too much, so that the Nutella swirl remains prominent.
Bake in the oven for 5 minutes, and then lower the temperature to 350 F (177 C) WITHOUT removing the muffin pan out of the oven.
Bake for an additional 15 minutes or until a toothpick inserted in the centre comes out clean.
Let the muffins cool completely before taking them out of the muffin pan.