1. Preheat oven to 350 degrees and butter a 9x13 baking sheet and line with parchment paper. Grease the parchment with butter.

2. In a medium bowl, sift the flour, baking soda and salt.

3. In a mixer, beat the melted butter, brown sugar, and superfine sugar. Beat in the vanilla, egg and egg yolk until light and creamy.

4. Mix in the dry ingredients until just blended and crumbly dough forms.

5. Gently press the dough into the bottom of the pan, sprinkle with chocolate chips and press down lightly.

6. Bake for 15 minutes until the dough is just cooked, but still soft.

7. Let cool on a wire rack.

8. Turn up oven temperature to 400 degrees.

9. Line a rimmed baking sheet with parchment paper and pour in the sugar.

10. Bake for about 5 minutes until the edges of the sugar are just beginning to melt.

11. Make sure which and mixer bowl are free from grease and pour the egg whites in.

12. Which on low at first, allowing small bubbles to form, then increase the speed to high and continue whisking until the egg whites form stiff peaks and the bowl can be turned upside down without the eggs falling out.

13. While whisking at high speed, add spoonfuls at a time of the sugar, ensuring the whites come back to stiff peaks before the next addition. Avoid the large chunks of caramelized sugar from the edge of the pan.

14. Mound the meringue onto the cookie base and spread it evenly.

15. Cut a piece of parchment paper the same size as the pan and lightly press it not the meringue.

16. Turn down the oven to 350 degrees and bake for 10 minutes.

17. Remove the parchment paper and bake for 5 more minutes.