Melt butter over medium heat, avoiding as much evaporation as possible.

Add both sugars and hot melted butter to a bowl, then whisk until combined and sugar is starting to dissolve, 2 minutes. Set aside and allow to cool 5 minutes.

Add water, vanilla extract and beaten egg to the butter and sugar blend and whisk well to combine and aerate, 1 minute.

In a medium bowl, whisk together the flour, baking powder, baking soda and salt. Add the dry ingredients to your wet mix and stir until combined. Fold in chopped chocolate and allow to rest 20 minutes.

Roll 3 tablespoons of dough into loose balls and arrange on a parchment lined baking sheet. Once all dough is rolled, wrap in another layer of parchment paper and allow to rest in the refrigerator overnight and up to 24 hours.

When ready to bake, preheat oven to 325F. Arrange cookies on a parchment lined baking sheet, leaving enough room for each ball to spread to 3x diameter. Bake until cookies have risen and begun to spread, around 5 minutes.

Use oven mitts to remove the cookie tray from the oven and drop it flatly on the open oven door to 'bang' the cookies. This will deflate the initial rise and result in lovely surface ripples with a toffee sweet crisp edge and soft, gooey interior in the finished cookie – divine!

Return cookies to the oven and continue to bake for a total of 15-18 minutes, banging again another 2-3 times.

Remove cookies from the oven just shy of desired doneness, usually around the 16 minute mark. Immediately garnish with a pinch of flaky sea salt.

Cool on the baking tray 5 minutes, then remove to a cooling rack and allow to fully cool and crisp before serving or storing in an airtight container. Enjoy!