Beat 1/2 sticks butter, 3/4 cup dark brown sugar and 3/4 cup granulated sugar until fluffy; beat in 1 teaspoon vanilla and 2 eggs. Whisk 2 1/2 cups flour, 3/4 teaspoon baking soda and 1 teaspoon salt, then stir into the butter mixture. Add 2 cups assorted chips (such as butterscotch, white, mini and/or bittersweet) and chill 30 minutes. Roll into balls and bake 8 to 12 minutes at 350 degrees.