In a large bowl, whisk together the mashed banana and peanut butter until smooth. Stir in the eggs until evenly combined. Next, stir in the maple syrup, chia seeds, vanilla, and cinnamon.
Sprinkle the baking soda, then the oat flour, over the top. Fold to combine. Last, fold in the pepitas, cranberries, and raisins. The batter will look very liquidy.
Place the bowl in the refrigerator to chill and set for at least 4 hours, or cover with plastic and refrigerate overnight.***
When ready to bake, place a rack in the center of your oven and preheat the oven to 375 degrees F. Line a baking sheet with parchment paper or a silicone baking mat. With a large cookie scoop or spoon, portion the batter by 1/4 cupfuls onto the prepared cookie sheet. If needed, shape them lightly with your fingers so that they are round and slightly flat on top.
Bake for 12 to 14 minutes, until the cookies feel dry and set on the top and edges and a toothpick inserted into the center comes out clean. Let cool on the pan for 10 minutes, then transfer to a wire rack to finish cooling completely.
TO STORE: Store leftover cookies at room temperature for up to 1 week.
TO FREEZE: Freeze the cookies in an airtight container for up to 3 months.
PROTEIN BOOST: I have not tried adding protein powder to these cookies. I think you could experiment with a tablespoon or two, but since I haven't tested the recipe this way, I can't be certain. If you do decide to play around with adding protein powder, I'd love to hear how it goes.
*FOR SWEETER COOKIES: As written, these cookies are not super sweet. If you desire a sweeter cookie, add 1 tablespoon of additional maple syrup.
**HOMEMADE OAT FLOUR: To make your own oat flour, pulse 3/4 cup oats in a food processor until they are well ground.
***TIP: I found that 4 hours of refrigeration time was sufficient for the cookies to set and be thick and puffed like in the photos. Ben's mom found that she needed to chill them overnight or the cookies came out flat. The thickness may vary with your oven, but if you want to be 100% sure of having thick, puffy cookies, I'd suggest overnight refrigeration.