Preheat the oven to 325° F. Line cookie sheets with parchment paper or a Silpat Mats.
Sift together the flour, baking soda and salt; set aside.
In a medium bowl cream together the melted butter, brown sugar and white sugar until well blended. Beat in the vanilla, egg and egg yolk until light and creamy.
Mix in the sifted ingredients until just blended. Stir in the chocolate chips by hand using a wooden spoon. If your butter was still hot when you added it, your dough may be quite wet at this point. If this is the case, let it rest at room temperature for a couple of minutes and then it should be cool enough to scoop into cookies.
Roll a scant half-cup of dough into a ball,, Holding dough ball in your hand, divide it into 2 equal halves and put it on your cookie sheet. Be sure that they are taller rather than wider.
Bake - reversing ½ way through cooking time until cookies are light golden brown and outer edges start to harden but centres are still soft and puffy (approximately 11 - 14 minutes). DO NOT OVERBAKE!
Cool cookies on cookie sheets until you are able to lift them without breaking. Transfer to wire rack to cool.