In a large mixing bowl, beat the softened butter and both sugars until creamy. Add egg and beat just until blended, scraping side of the bowl often. Beat in vanilla.
In a separate bowl, mix together the Cup4Cup, baking soda and salt. Gradually add to the batter, stirring until incorporated. Stir in the chocolate chips or chunks.
Using a medium cookie scoop (or a generously heaping tablespoon) scoop out about 16 rounds of dough and set them on a plate. Cover and chill for 30 minutes or preferably longer. Overnight is best.
Preheat oven to 350 degrees F. Line a baking sheet with parchment paper. If you have a convection oven, you can bake at 350 or 330 degrees convection.
Arrange the chilled dough balls about 2 ½ inches apart. Bake one sheet at a time for 10-14 minutes or until edges are golden. Remove cookies to wire racks and cool completely.