4 Chop the remaining chocolate into chips.
5 Beat butter and sugars together until pale and fluffy, about 4 minutes. Add the egg and beat in for about 1 minute. Add vanilla extract and beat to incorporate. Beat in the melted chocolate.
6 Sift together flour, baking soda, and salt.
7 Add the mixture all at once to the butter mixture. Beat on a low speed until just incorporated. Finally mix in the chocolate chips.
8 For each cookie, spoon about 2 tbsp of the mix onto the tray, gently flatten the mix and sprinkle with the salt flakes. Leave about 5cm of room between each cookie.
9 Bake for 18 minutes. Remove from the oven and allow to cool on the tray for 5 minutes before removing to a wire rack to cool completely.
