Preheat oven to 170 C / Gas 3. Line a baking tray with parchment.
In a large bowl sift together flour, salt and bicarb.
In a separate bowl beat together melted butter, brown sugar, egg, egg yolk and vanilla extract. Gradually add flour and chocolate chips and mix together. Make large mounds of cookie dough, about 3 to 4 tablespoons each, and place on the prepared tray, spacing 8cm apart on the tray.
Bake for 15 to 17 minutes. Cool slightly on the tray then remove to a wire rack to cool completely. Serve and enjoy!