Preheat oven to 325 degrees.

In a bowl, beat together butter, peanut butter, sugar and banana until smooth. Bits of banana are ok though.

Then beat in the egg yolk and vanilla until combined.

Blend in the flour, salt, and soda just until combined.

Fold in the chocolate chips.

Using a cookie scoop or spoon, drop golf ball sized balls of dough onto the baking sheet, place 2 inches apart.

Bake for 14-18 minutes until the edges of the cookie turn golden brown. The center of the cookie can look under done. Don't worry.

Allow the cookies to cool on the sheet for 2 minutes and then cool completely on a rack. This aren't the kind of cookie you eat warm, they will be doughy. However, if you allow them to cool completely they will be perfect. Makes 2 dozen.