Heat oven to 350 degrees. Line a 15x10.5" pan with foil and spray with non-stick spray.
Whisk all ingredients except for the flour and chocolate chips. Gradually add in flour until just blended. Mix in half the chocolate chips.
Spread the batter into the prepared pan and sprinkle remaining chips on top. Bake 15-20 minutes, until a wooden toothpick inserted in center comes out clean.
Cool completely. I've even stuck the entire pan into the freezer so that they'd cut cleaner! Once cool, cut into squares.
If you're preparing these for school lunches, I suggest bagging them individually and freezing them like that. If you freeze prior to cutting, the chocolate on top doesn't make a mess in the baggie.
