In a large bowl, sift together flour, sugars, cinnamon, ginger, nutmeg, baking soda, baking powder, and salt.
In a second bowl, mix together eggs, butter, and pumpkin. Slowly add the pumpkin mixture to the dry ingredients. Add in 1 ½ cups butterscotch chips.
Spray a muffin tin (or use muffin tin liners) with cooking spray. Pour batter into the muffin tins, so they're about ⅔ full. Sprinkle remaining butterscotch chips on top.
Bake in the preheated oven for 15-18 minutes, or until a toothpick inserted in the center comes out clean.
Notes
We think the pumpkin and butterscotch make a winning combination, but you could definitely substitute other ingredients in their place. We like to substitute in the following ingredients: chocolate chips, chopped walnuts, white chocolate chips, crumb topping, topped with glaze, or sprinkled with powdered sugar. Slightly adapted from this recipe.