Beat butter and sugars. Mix in the sour cream, bananas, vanilla and egg. Add the remaining ingredients.
Use a cookie sheet with parchment paper. Using a small scoop, drop dough onto paper. Bake in a 350 degree oven for 10-12 minutes. Cool and frost if desired!
For the frosting:
Beat cream cheese and butter until fluffy. Add remaining ingredients and beat until smooth. Spread between two like-sized cookies or on top of each cookie. Add chopped walnuts if desired.
Notes
Instead of whoopie pies, just pipe a dollop of frosting onto the tops of each cookie.
You can also add in some chopped nuts (walnuts or pecans) to add a little texture and nutty flavor to these banana cookies.
Of course you also can't go wrong with adding chocolate chips. I think banana chocolate chip cookies sound incredible!
Store banana cookies in airtight container in the refrigerator (if frosted or whoopie pies).
Freeze banana cookies in airtight container for up to 3 months, with or without frosting.