Preheat the oven to 350°F. Spray the bottom and sides of 2 non-stick metal 9 x 5 OR 8 x 4-inch standard loaf pans with baking spray or butter and flour.
Using an electric mixer cream together the peanut butter, softened butter and vanilla for 2 minutes until fluffy.
Add the granulated and brown sugars. Beat on medium-high for 2 minutes or until fully combined.
Add the eggs one at a time mixing well after each addition. Increase the speed of the mixer and beat for 30 seconds until light beige in color. Stop and scrape the sides of the bowl periodically.
Lower the speed of the mixer and gradually add the flour alternately with the yogurt beginning and ending with flour. After all has been added, beat just until fully combined scraping the bottom and sides of the bowl.
Fold in the mashed banana and Reese's by hand until fully incorporated.
Use a measuring cup to divide the batter between the two pans.
Bake for 35 minutes then check for browning. Lay foil on top, if needed.
Continue to bake another 15-20 minutes or until a toothpick inserted into the center comes back clean.
Cool in the pan for 15 minutes them remove from pans and place on a cooling rack to cool completely.