Step 1

Preheat the oven to 350 degrees and arrange three racks evenly spaced in the oven. (See note below.)

Step 2

In a mixing bowl or the bowl of your stand mixer, beat the butter on medium speed until creamy, 3 minutes. Add granulated and brown sugar, and continue beating until light and fluffy, 2-3 minutes.

Step 3

Scrape down sides of bowl with a rubber spatula, then add the egg, vanilla, and 2 tablespoons of warm water and mix until just combined on low speed.

Step 4

In a separate bowl, whisk together the flour, baking soda, and salt. While mixing on low, slowly add the flour mixture to the wet ingredients, followed by the chocolate (including any fine chocolate dust) until just combined. Use a rubber spatula to mix well.

Step 5

Scoop dough out onto a sheet pan, using a 2 1/4 inch ice cream scoop or 1/3 cup measuring cup. (This was yield 12 scoops.)

Step 6

Freeze dough for exactly 15 minutes, then place 4 balls of dough on a sheet pan lined with parchment paper. Repeat with remaining dough.

Step 7

Bake 10 minutes, until cookies are slightly puffed in the center. Remove from oven and bang pan on the stovetop until center of cookies deflate. Return to oven for 3 minutes, then bang on stovetop again. Continue baking and banging every 3 minutes, until cookies have been in the oven for 18-20 minutes total and are golden brown around the edges. Rotate pans so cookies bake evenly.

Step 8

Sprinkle cookies with fleur de sel and let cool completely on the pans.

Step 9

Note: If your oven only has two racks, you can bake these cookies in two batches, but don't freeze any batch of dough longer than 15 minutes.