Preheat the oven to 165 degrees C/325 degrees F. Grease cookie sheets or line with parchment paper.
Sift together the flour, bicarb and salt; set aside.
In a medium bowl, cream together the melted butter, brown sugar and caster 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. Drop cookie dough onto the prepared baking trays, with each cookie around 4 tablespoons of dough (for smaller cookies, drop 1 rounded tablespoonful and adjust baking time as necessary). Do not flatten the dough. Cookies should be about 8cm apart.
Bake for 15 to 17 minutes in the preheated oven, or until the edges are lightly toasted. Cool on baking trays for a few minutes before transferring to wire racks to cool completely.
Can't find chocolate chips?
Make your own using your favorite chocolate bar. Using a sharp knife, roughly cut into 1 cm size pieces.