Preheat the Oven and Grease the Baking Sheets - Preheat the oven to 350 degrees Fahrenheit. Grease your baking sheets with cooking spray, or if you prefer line them with parchment paper.
Beat Butter, Brown Sugar, Egg, Peanut Butter, and Vanilla Extract - In a large bowl, beat together the butter, brown sugar, egg, peanut butter and vanilla extract until smooth.
Combine the Garbanzo Flour, Cornstarch, Baking Powder, and Salt - In a medium mixing bowl, combine the garbanzo flour, cornstarch, baking powder, and salt. Mix well until combined.
Combine the Wet and Dry Ingredients - Slowly add the dry ingredients into the wet ingredients, mixing until a dough forms.
Add Chocolate Chips and Oats - Using a rubber spatula, carefully fold in the chocolate chips and oats. If desired, fold in nuts as well.
Chill the Dough - Chill the dough for 15 minutes in the fridge.
Bake the Cookies - Scoop the cookie dough into tablespoon-sized balls. Arrange them on the baking tray so they are two inches apart.
Bake the cookies for nearly 10-13 minutes, or until golden brown. Allow them to cool on the baking trays for 2-3 minutes before transferring to a wire rack to fully cool.