Preheat the oven to 350 degrees F. Line 2 to 3 baking sheets with parchment paper or re-usable baking sheets (silpats).
Whisk the flour, salt, and baking soda together in a medium bowl, and set aside.
In a large bowl, cream the butter and sugars with a hand held electric mixer, until light and fluffy. Beat in the egg and then the vanilla. Gradually add the dry ingredients to the creamed mixture. Stir in the chopped chocolate.
To form the cookies, scoop heaping tablespoons of the dough and roll by hand into balls. Place the balls about 2 inches apart on the baking sheets. Flatten the dough slightly with your fingertips. Bake until light brown, about 12 to 15 minutes. (If baking 2 sheets at a time, rotate the pans halfway through baking.) Transfer cookies to a rack to cool. Lightly dust the cookies with confectioners' sugar, if desired.