Using an ice cream scoop (about 1/4 cup capacity), scoop 12 cookies and place them on a pan or a large plate, the one next to the other. Place the chocolate pieces you have left on top of each cookie, cover with cling film and refrigerate for 3-4 hours or overnight.
Roll each cookie into a ball and transfer to the pan, leaving about 2-3 inches distance between each cookie. Sprinkle the cookies with some sea salt flakes and bake for 11 minutes. The cookies will puff up a bit.
Take the pan out of the oven and
TAP/BANG IT 2-3 TIMES ON THE COUNTER
for the cookies to deflate and settle. This will give them a bakery-style look. Let them cool for 5 minutes and transfer to a rack to cool completely.