1Heat oven to 350°F (325°F for dark or non-stick pans). Grease bottoms only of 2 (8x4-inch) loaf pans with shortening.
2In small microwavable bowl, microwave peanut butter and butter uncovered on High 30 to 45 seconds or until butter is melted. Stir until mixture is smooth.
3In large bowl, beat sugar and eggs with electric mixer on medium speed 1 minute or until blended. On low speed, add peanut butter mixture; beat well. In another bowl, mix flour, baking soda and salt. Add flour mixture alternately with sour cream to peanut butter mixture, beating on low speed until blended. Stir in bananas, chocolate chips and vanilla until blended. Divide batter between pans.
4Bake 1 hour 10 minutes to 1 hour 15 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes; remove from pans to cooling racks. Cool completely, about 2 hours.