Preheat oven: Preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius).
Mix banana with wet ingredients: To prep the cookies, first peel the ripe banana and place it into a bowl. Then add softened vegan butter, light brown sugar, and vanilla extract. Then, using your handheld mixer, beat until the banana, sugar, and vanilla are whipped into the butter, about 2 minutes.
1 cup ripe banana, ¼ cup vegan butter, ⅔ cup light brown sugar, 1 teaspoon vanilla extract
Add dry ingredients: Add flour, cinnamon, baking soda, and salt to the mixing bowl. Mix until well combined, mixture should be soft but not runny.
¾ cup all purpose flour, 1 teaspoon cinnamon, ½ teaspoon baking soda, ¼ teaspoon salt
Add oat: Next, add the rolled oats to the bowl and mix until well combined with the other ingredient mixture. The final cookie batter should be thick and somewhat wet; it should not be dry and crumbly. If your batter is on dry side, add a small amount of plant-based milk (about 1-2 tablespoons) to get to desired consistency (see photo steps in recipe post step four, as an example).
1 ½ cups rolled oats, 2 tablespoons plant-based milk
Add cookie dough to baking sheet: Scoop 1 tablespoon of cookie batter for each cookie onto a lined baking sheet; the batter should make about 12 cookies. For a thinner cookie, press the batter down with a spatula before baking.
Bake cookies: Place the baking sheet in the oven to bake for 10-13 minutes. For chewier, softer cookies, bake for only 10 or 11 minutes; the cookies may not look done, but leave them on the baking sheet for 2 minutes after removing them from the oven and they will firm up but remain soft. For firmer cookies, cook for 12-13 minutes. Remove cookies to a cooling rack and let cool before eating.