In a large mixing bowl, combine the chocolate cake mix, eggs, and vegetable oil. Add vanilla extract if using. Mix until well combined and a dough forms.

If adding mix-ins like chocolate chips or nuts, fold them into the dough until evenly distributed.

Take spoonfuls of the dough and roll into balls, about 1 inch in diameter. If the dough is sticky, lightly oil your hands or chill the dough for a few minutes to make it easier to handle.

Place parchment paper in the air fryer basket to prevent sticking. You can also lightly spray the basket with cooking spray. Arrange the cookie dough balls in the basket, leaving enough space between them for expansion. You may need to cook in batches depending on the size of your air fryer.

Cook the cookies at 350°F (175°C) for about 8-10 minutes, or until they are set and slightly crisp on the edges. The exact time might vary based on your air fryer model and how chewy or crispy you prefer your cookies.

Once done, let the cookies cool in the basket for a few minutes before transferring them to a wire rack to cool completely. They will firm up as they cool but remain soft and chewy on the inside.