An easy brownie recipe that starts mix a mix. For a half batch (8-inch pan), use your scale and weigh out half a can of condensed milk and half bag of chocolate chips.
Preheat oven to 350 degrees F. Spray a shiny 13x9 inch metal baking pan with cooking spray (bottom only). If you are using a dark pan, preheat the oven to 325 degrees F. Alternatively, line with foil or parchment and grease bottom only.
Prepare the brownie mix as the package directs.
During last 5 to 10 minutes of baking, start preparing topping. Cook condensed milk and chocolate chips together in a saucepan over medium-low to medium heat. Stir to melt chips, then remove from heat and stir in vanilla.
Remove brownies from oven and immediately spread topping over brownies. Set the pan on a rack and let them cool completely, then transfer to the refrigerator and chill for an hour to set topping. Cut into bars.