Preheat your oven to 350°F (175°C) and prepare an 8x8 or 9x9 baking pan with parchment paper, greased lightly.

In a large mixing bowl, combine the yellow cake mix, melted butter, and large eggs. Mix until smooth, about 2-3 minutes.

Gently fold in the semi-sweet chocolate chips, ensuring they are evenly distributed. Add any optional mix-ins if desired.

Pour the batter into the prepared baking pan, spreading it evenly. Sprinkle extra chocolate chips on top if using.

Bake in the preheated oven for 22-26 minutes until the edges are golden brown and the center is slightly soft.

Remove from the oven and let cool completely at room temperature. Lift out with parchment and slice into squares.