Preheat oven to 350° F. Soften butter to room temperature. Line muffin tin with cupcake wrappers.
Using a hand mixer, beat the eggs on medium speed; add the butter and mix thoroughly.
Add mashed potatoes, maple syrup, and vanilla.
In a separate bowl, mix together flour, baking soda, baking powder, cinnamon, nutmeg, salt, and cocoa.
Gradually mix dry ingredients into the wet ingredients, stirring by hand; do not over-mix. Fold in pecans (or walnuts) if desired.
Divide batter among muffin cups and bake for 20-25 minutes or until a toothpick inserted into the center of a muffin comes out clean.