First: Preparation

1. Preheat the oven to 350°F (175°C) and line two baking sheets with parchment paper.
2. Gather all ingredients and ensure the butter is at room temperature.

Second: Making the Dough

1. In a large mixing bowl, cream the butter until light and fluffy (about 2-3 minutes) using a hand or stand mixer.
2. Add the egg and vanilla extract, mixing until well combined.
3. Gradually incorporate the muffin mix, stirring just until the dough comes together. Avoid over-mixing to keep the cookies soft.

Third: Shaping and Baking

1. Using a cookie scoop, portion out dough balls onto the prepared baking sheets.
2. Bake for 11-13 minutes, or until the edges are golden brown but the centers remain soft.
3. Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack.