1-First Step: Preheat your oven to 350°F. Grease a 9×13-inch baking pan with cooking spray or line with parchment paper for easy removal. This prevents sticking and ensures even baking. Parchment also simplifies cleanup, a win for busy schedules.

2-Second Step: In a large mixing bowl, combine 1 (15.25-oz) box cake mix, 1/2 cup melted unsalted butter, 1 large egg, and 1 teaspoon vanilla extract if using. Stir with a wooden spoon or spatula until a thick dough forms. It might look crumbly at first, but keep mixing for 1-2 minutes until smooth. The warmth from melted butter helps everything incorporate quickly. This step takes just 2 minutes and creates the foundation for chewy cookies. Avoid overmixing to keep the texture light.

3-Third Step: Fold in 1 cup of your chosen add-ins, like semisweet chocolate chips, chopped nuts, or M&Ms. Use a spatula to gently mix until evenly distributed. For layered effect, press half the dough into the pan, sprinkle add-ins, then top with remaining dough. Chill the dough for 10 minutes in the fridge if it’s too sticky to handle. This makes pressing easier and prevents spreading during baking.

4-Fourth Step: Transfer the dough to the prepared pan. Use slightly wet hands, a spatula, or the back of a spoon to press it evenly across the bottom. Aim for a uniform 1/4-inch thickness. Wet hands prevent sticking and give a smooth surface. For a crackly top, sprinkle a bit of extra sugar or sea salt before baking. This adds visual appeal and subtle crunch.

5-Fifth Step: Bake at 350°F for 18-22 minutes. Watch for edges to turn light golden and the center to set but still soft. Chocolate cake mixes may need 2-3 extra minutes. Avoid overbaking to maintain chewiness. Optional: Broil for 1-2 minutes at the end for a shiny, crackly top. Keep a close eye to prevent burning.

6-Final Step: Remove from oven and cool in the pan on a wire rack for 30 minutes. Full cooling takes about 1 hour to firm up. Lift out using parchment, then cut into 24 squares. Store as directed below.