Preheat oven to 180 C / 350 F. Line a 12 hole muffin tin with muffin cases. Set aside.
Place flour, granulated (caster) sugar, brown sugar, baking soda and ground cinnamon or pumpkin pie spice in a large bowl. Whisk to combine.
In another bowl, place pumpkin purée, eggs, oil and milk. Whisk to combine.
Make a well in the dry mixture. Add pumpkin-egg mixture. Fold in gently to create a smooth batter. Do not over mix the batter. The batter will be slightly thick.
Divide batter among the muffin cases. Bake for 20-25 minutes, until risen, firm to the touch and a skewer inserted in the middle comes out clean.
Leave the muffins in the tin to cook for a few minutes and transfer to a wire rack to cool completely.