Preheat your oven to 350°F.
In a medium mixing bowl mix together flour, baking powder, baking soda, salt, cinnamon, nutmeg, and the white and brown sugars.
In a small bowl, mix the milk and the sourdough starter until well blended.
Add the melted butter, vanilla and egg to the starter mixture.
Pour the liquid ingredients into the dry ingredients and add the chopped pecans and mix that all up, just until it's combined.
Using spoons or a cookie scoop, scoop the mixture evenly into 12 muffin cups.
If you're not using papers, make sure you grease the pan, so they don't stick.
Bake for 20 to 25 minutes.
After baking, remove them from the pan, slice them open, and slather on the butter.