Spray a 9x13 baking pan* with cooking spray or line with parchment paper. Preheat the oven to 350º Fahrenheit.
In a large microwave safe bowl, melt the butter completely.
Add the brown sugar and use a hand mixer to mix the sugar and butter together well.
Add the eggs, one at a time, mixing between each addition.
Add the flour, baking powder and salt, then mix again just until combined. Scrape the sides of the bowl as needed.
Fold in the chocolate chips. The batter will be very thick.
Spread in the prepared pan. Bake for 25 minutes or until very lightly browned around the edges.
These are meant to be gooey bars. If you don't want them gooey and would like them more crisp, go ahead and bake them a few minutes longer.
Cut into squares once they are cool.
Store in an airtight container at room temperature.
You can freeze them if you'd like for up to 2 months.
Video
Notes
*You can use an 11x14 or even 10x15 baking pan for thinner bars. They won't take quite as long to cook so watch them carefully.The calories shown are based on the recipe being cut into 20 pieces, with 1 serving being 1 cookie bar. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information.**