Preheat oven to 165 degrees C. Grease baking trays or line with baking paper.
Sift together the flour, bicarbonate of soda and salt and set aside.
In a medium bowl, mix the melted butter, brown sugar and white sugar until well blended. Beat in the vanilla, egg and egg yolk until light and creamy, then add the sifted ingredients until just blended. Stir in the chocolate chips by hand using a wooden spoon. Drop cookie dough 1/4 cup at a time on to the baking trays. Cookies should be about 8cm apart.
Bake for 15 to 17 minutes, or until the edges are lightly browned. Remove from oven and allow to cool on trays for a few minutes before transferring to wire racks to cool completely.