The proper way to measure flour using measuring cups is to aerate it first. This is done either by sifting flour, or aerating it by fluffing it up and whisking it well, then spooning it into the measuring cup, then carefully removing any excess flour with a knife. If you just stick that measuring cup in the bag of flour and scoop some out, you will get a lot more flour than what the recipe calls for. Do aerate the flour, or you will end up with dry dough! :)

Pre-heat oven to 350 degrees F. In a large bowl, combine together the flour, baking powder, baking soda, cinnamon, and salt.

In a separate bowl, mash the banana. Add the egg, oil, brown and granulated sugars, yogurt, and vanilla and whisk to combine.

Add the banana-egg mixture to the flour mixture and stir until just combined. Fold in the oats, then fold in the chocolate chips.

Line two baking sheets with parchment paper. Take a tablespoon of dough, form a ball and drop the cookie dough ball on the prepared baking sheet. Repeat, spacing the cookie dough balls about 2 inches apart. At this point, I would refrigerate baking sheets with cookie dough balls for about an hour to chill the dough. This will ensure that cookies, when baked, will not flatten out, and that they will remain tall, so that we end up with thick and chewy cookies!