Yield: 10 cookies
Time: 30 minutes, plus chilling
2 cups all-purpose flour
1/2 teaspoon baking soda
3/4 teaspoon salt
250ml unsalted butter (2 sticks), room temperature
1 1/2 cups sugar
1/4 cup packed light or dark brown sugar
1 1/2 teaspoons pure vanilla extract
170g bittersweet chocolate (about 60 percent cacao solids), chopped into coarse pieces, bits and shards
Adjust an oven rack to the middle position. Heat the oven to 350 degrees. Line 2 baking sheets with aluminum foil, parchment paper or nonstick baking mats.
In a small bowl, whisk the flour, baking soda and salt.
In the bowl of a stand mixer fitted with a paddle, beat the butter on medium until creamy. Add the granulated and brown sugars and beat on medium until light and fluffy, 2 to 3 minutes. Add the egg, vanilla and 2 tablespoons water, and mix on low to combine. Add the flour mixture, and mix on low until combined. Add the chocolate and mix on low into the batter. (At this point, the dough can be refrigerated for several hours or overnight.)
Form the dough into 99g (a heaping 1/3 cup each). Place 4 balls an equal distance apart on a prepared pan, and transfer to the freezer for 15 minutes before baking. After you put the first baking sheet in the oven, put the second one in the freezer.
Place the chilled baking sheet in the oven and bake 10 minutes, until the cookies are puffed slightly in the center. Lift the baking sheet and let it drop down against the oven rack, so the edges of the cookies set and the inside falls back down. (This will feel wrong, but trust me.) Bang it down, if necessary, to make the center fall.
After the cookies puff up again, 2 to 3 minutes later, repeat lifting and dropping the pan. Repeat a few more times, every 3 minutes, to create ridges around the edge of the cookie. Bake 16 to 18 minutes total, until the cookies have spread out, and the edges are golden brown, but the centers are much lighter and not fully cooked.
Transfer the baking sheet to a wire rack; let cool before removing the cookies from the pan.
Repeat with remaining cookies, using the first sheet pan for the third batch of cookies.