Mix the melted butter (110g) with the sugars (100g brown sugar and 60g cane sugar) for 2 minutes in a medium bowl.
Add the egg and vanilla paste (1 tsp). Whisk until creamy (about 1 minute).
Fold in the flour (140g), baking soda (½tsp), and salt (1tsp) until no streaks are visible.
Chop the chocolate (150g) into various sized pieces.
Add 110 grams chopped chocolate to the batter, and mix.
Use a cookie scoop or spoon to shape the cookies (I got 8 in total).
Rest the scooped balls on a plate in the fridge for at least 1 hour.
Preheat the oven to 170°C (338°F) fan.
Place the scooped cookies on a lined baking sheet spaced apart (I baked 4 each time).
Top with the remaining chopped chocolate.
Bake for 10-11 minutes, until golden brown on the edges and barely set in the center.
Bang the baking sheet on a hard surface just as the cookies come out of the oven (to release any trapped air).
Then, shape them with a burger shaper or glass while still hot from the oven (or use a spoon).
Sprinkle with flaky sea salt.
Leave the cookies to cool for 2-3 minutes, then transfer to a cooling rack.
Bake the remaining cookies in the same way. Enjoy.