1. Preheat oven to 450~ .
2. Place paper liners in muffin tin,set aside. Vombine flour,baking powder,cinnamon,and nutmeg in medium bowl.
3. toss to blend with fork.set aside. Peel banana,break into small pieces,and set it aside on wax paper.
4. In large mixing bowl,combine peanut butter and sugar.
5. Mix at medium speed to blend.Stop when necessary to scrape sides of bowl with rubber scraper.
6. Add eggs and blend.Add banana and blend.Add flour mixture in two stages and mix until it is completely incorporated.
7. Do not over mix. Add sour cream and blend. Spoon batter into muffin cups until they are about 3/4 fulled.
8. With mitted hands,carefully place pan in oven and bake for 25 minutes.
9. Turn oven off and with mitted hands,carefully remove muffin pan and set it on cooling rack for 10 minutes.
10. With your mitts on,carefully tip tin on its side to let muffins fall out.
11. If there is a stubborn muffin,use table knife to loosen it.
12. Once muffins are completely cool wrap them in plastic wrap and freeze.