Preheat oven to 180°C. Line a large cookie tray with baking paper.

In a bowl, combine melted butter, olive oil, egg, both sugars, salt, and vanilla extract. In a separate bowl, whisk together flour and baking powder. Fold the flour mixture into the wet ingredients until just combined. Fold in chopped chocolate.

Scoop dough using a small ice-cream scoop, keeping around 5cm between each cookie as they spread. Bake for 12 minutes, or until light golden brown. Allow to cool on tray for 5 minutes before moving to a wire rack to cool completely. Sprinkle with a sea salt.