01 -
Preheat oven to 350°F. Grease a 9×13-inch baking pan.
02 -
In a large microwave-safe bowl, melt the butter in 30-second intervals until fully liquid. Allow to cool slightly to prevent cooking the eggs.
03 -
Add eggs to the melted butter and whisk until mixture is smooth and fully combined. If using, add vanilla extract at this stage.
04 -
Stir the yellow cake mix into the butter and egg mixture. Mix until a thick dough forms.
05 -
Add the chocolate chips and stir until evenly distributed through the dough. If adding salt, include it with the chocolate chips.
06 -
Spread the dough evenly in the prepared 9×13-inch pan using a spatula or clean hands. Smooth the surface.
07 -
Bake for 20 to 23 minutes, until bars are golden around the edges and just set in the center. For thicker bars in a smaller pan, bake for 25 to 28 minutes.
08 -
Let bars cool in the pan for 15 minutes before slicing. Serve warm and gooey or after fully cooling.