Mix the melted butter with the sugars for 2 minutes in a medium bowl.
Add the egg and vanilla paste. Whisk until creamy.
Fold in the flour, baking soda, and salt until no streaks are visible.
Chop the chocolate 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.