1️⃣ Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.
2️⃣ In a large bowl, mix the brownie mix, mashed banana, oil, egg, vanilla extract, and flour until fully combined. The dough will be thick.
3️⃣ Fold in chocolate chips (if using).
4️⃣ Scoop out tablespoon-sized balls of dough and place them 2 inches apart on the baking sheet.
5️⃣ Bake for 12-15 minutes, or until the edges are set but the centers are still slightly soft.
6️⃣ Let cookies cool on the pan for 5 minutes, then transfer to a wire rack to cool completely.
7️⃣ Enjoy these chewy, chocolatey cookies with a glass of milk or coffee! ☕