Cream the butter and sugars in an electric mixer until light and fluffy.
Add in the egg yolk. Mix well.
Add in the banana and the vanilla extracts. Mix well.
Combine the flour, milk powder, baking soda and salt in a bowl and mix well.
Add the flour mixture to the butter mixture and mix until combined.
Fold in the chocolate chips, graham wafers and banana chips.*
Form balls with the dough and place on a baking sheet (I used a 2” cookie scoop).
Bake at 350 for 9-11 minutes.**
Notes
*I reserve a few of these add-ins and sprinkle them on top of the cookie dough balls before they go into the oven.**Check the cookies at 8 minutes and if you want them flatter, remove the baking sheet and bang it on the counter a few times, then return to the oven to finish baking.