Preheat the oven to 375 degrees F. Grease a 10 inch oven-proof skillet.
In a large mixing bowl, beat the sugars and butter until blended. Beat in the vanilla and the eggs. Reduce speed to low and beat in the baking soda and salt, then add the flour and mix using lowest speed of the mixer. Stir in the chips.
Scrape the batter into the skillet and spread evenly. Bake on center rack for about 30 minutes. Let cool for 15 minutes, then slice.
Notes
This recipe works very well with tub style spreads as long as they are the kind with 90 to 100 calories per oz (so enough fat). The lower calorie ones won't work because they have more water, but the tub style spreads with fat (Earth Balance, Olivio, Melt) and the sticks such as Country Crock and I Can't Believe it's Not Butter should give you skillet cookies with a crisp exterior and softer interior. If you don't have a 10 inch skillet you can make the full batch, set aside about a cup of the batter and use a 9-inch springform pan.