Preheat oven to 350° degrees. Grease 9- x 5-inch loaf pan and line with parchment paper.
Whisk together flour, baking powder, baking soda, salt and nutmeg. In separate bowl, whisk together eggs, sugar, milk, melted butter and vanilla until blended. Whisk in bananas until combined; stir into flour mixture. Fold in chocolate chunks.
Scrape two-thirds of the batter into prepared pan; drop peanut butter by heaping teaspoonfuls evenly on top. Scrape remaining batter over top. Using a skewer or tip of a knife swirl peanut butter into batter (do not over-swirl). Smooth top.
Bake for an hour and 10 minutes to an hour and 15 minutes or until tester inserted into center comes out clean. Let cool completely in pan on rack. Wrap and store at room temperature for up to 2 days or wrap in heavy-duty foil and freeze for up to 2 weeks.