1-First Step: Preparation and Mise en Place Begin by preheating your oven to 350°F. This temperature is ideal for creating those crispy edges while keeping the center soft and gooey. While the oven heats up, line a baking sheet with parchment paper. This prevents the cookies from sticking and makes cleanup much easier. There is no need to grease the paper, as the butter in the dough provides enough release. Next, gather all your ingredients. Measure out the 1/2 cup of unsalted butter and melt it. You can do this in the microwave in short bursts or on the stove over low heat. Let it cool slightly so it does not cook the egg when mixed. Crack your egg into a small bowl to ensure no shell fragments get into the dough. Have your vanilla extract and chocolate chips ready and measured. Having everything prepared before you start mixing helps the process go smoothly.

2-Second Step: Mixing the Dough In a large mixing bowl, combine the 1 box of brownie mix, the melted butter, the egg, and the 1 teaspoon of vanilla extract. There is no need for a mixer; a sturdy spatula or wooden spoon works perfectly for this task. Stir the ingredients together until a thick, cohesive dough forms. It might seem stiff at first, but keep mixing until all the dry brownie mix is incorporated into the wet ingredients. Once the dough is uniform, fold in the 1 cup of semi-sweet chocolate chips. Mix them just until they are evenly distributed throughout the dough. Be careful not to overmix at this stage, as overworking the dough can lead to tougher cookies. The dough will be thick and rich, which is exactly what you want for that fudgy texture.

3-Third Step: Scooping and Shaping Using a cookie scoop or a tablespoon, portion the dough into balls. Aim for about 1.5 tablespoons of dough per cookie to get a standard size. Roll the dough gently between your palms to create smooth rounds. Place the dough balls onto the prepared baking sheet, spacing them about 2 inches apart. This spacing is crucial because the cookies will spread as they bake. If you prefer a thicker cookie, you can chill the dough balls in the refrigerator for 10 to 15 minutes before baking. This helps solidify the fat, resulting in less spread and a denser final product. However, if you are short on time, you can bake them immediately. Both methods produce delicious results, so feel free to choose based on your preference.

4-Fourth Step: Baking to Perfection Place the baking sheet in the center of your preheated oven. Bake the cookies for 10 to 12 minutes. Because brownie mix is denser than traditional cookie dough, the baking time is relatively short. It is important to keep a close eye on them during the last couple of minutes to prevent overbaking. You will know the cookies are done when the edges look set and matte, but the centers still appear slightly soft and shiny. They might look underdone, but this is the secret to a fudgy texture. The residual heat from the pan will continue to cook them as they cool. If you bake them until they are completely firm in the oven, they will turn cakey rather than chewy.

5-Final Step: Cooling and Serving Remove the cookies from the oven and let them cool on the baking sheet for 5 minutes. This resting period is vital. It allows the structure of the cookie to firm up enough so you can move them without them falling apart. During this time, they will deflate slightly and crack on top, creating that signature brownie cookie look. After 5 minutes, use a spatula to transfer the cookies to a wire cooling rack to cool completely. If you can resist, wait until they are fully cool to enjoy the best texture. However, serving them warm is a divine experience, especially with a glass of cold milk. The chocolate chips will still be molten, offering a luxurious mouthfeel that is hard to beat.