In a large bowl, combine the brown sugar, butter, banana, peanut butter, eggs and vanilla just until combined.
In a medium bowl, combine flour, baking powder and salt. Mix well and add to creamed mixture. Combine just until moistened and stir in chocolate chips.
Spread into a greased 13x9 inch baking pan. Bake for 18-20 minutes or until a toothpick inserted near the center comes out clean. Cool before cutting into bars.
Notes
Keep baking closer to the 18 minute mark if you like under baked gooey bars. Recipe adapted from Taste of Home Most Requested Recipes cookbook.