Using a stand mixer, combine butter, brown sugar, eggs and vanilla. Beat until creamy, about 2 minutes.
Gradually add flour, baking powder and salt. Mix until well combined.
Add one half chocolate chips and stir until well incorporated.
Evenly spread batter in an ungreased 9x13 inch baking dish. Evenly distribute reserved chocolate chips on top of batter and use palm of one hand to gently push chips into batter.
Bake for 30 to 40 minutes, until toothpick comes out clean, after being inserted into center of pan. Allow to cool thoroughly on a baking rack before cutting and serving.
Video
Notes
You can use 1/2 butter and 1/2 shortening for this recipe.
Substitute the chocolate chips for M&M's and you can turn these into holiday M&M cookie bars.
Be sure your eggs are at room temperature before adding them to the batter.