David Lebovitz's buckwheat chocolate chip cookies. Excerpted from L’Appart: The Delights and Disasters of Making My Paris Home by David Lebovitz. Copyright © 2017 by David Lebovitz. Published in the United States by Crown, an imprint of the Crown Publishing Group, a division of Penguin Random House LLC, New York. Reproduced by arrangement with the Publisher. All rights reserved.
In a large bowl, mix together the brown sugar, granulated sugar, and melted butter. Add the egg, egg yolk, and vanilla.
In a separate bowl, whisk together the all-purpose flour, buckwheat flour, baking powder, baking soda, and salt. Stir the dry ingredients into the butter-sugar mixture.
Mix in the chopped chocolate (and any small bits of chocolate), buckwheat groats, and nuts. Cover the bowl and chill overnight.
Remove the dough from the refrigerator at least 30 minutes before you plan to scoop the cookies.
Preheat the oven to 350ºF (180ºC). Line two baking sheets with parchment paper or silicone baking mats.
Use a spring-loaded ice cream or cookie scoop (or a tablespoon and your hands) to form the dough into 1½-inch (4cm) balls, and place them 2½ inches (6cm) apart on the baking sheets (you will likely need to bake the cookies in batches). Slightly flatten the tops with damp fingers and sprinkle with flaky sea salt.
Bake the cookies until light golden brown on top, about 12 minutes, rotating the baking sheets on the oven racks midway through baking. Remove the cookies from the oven and using a flat metal spatula (also called a pancake turner), tap the top of each cookie to flatten it, so each is about ½ inch (1.25cm) high. The bottom of the spatula may pick up some sticky chocolate, which can be wiped clean so the finished cookies have a neater appearance. Let cool on the baking sheets.
Once the cookies and baking sheets are cool, remove the cookies from the baking sheets and finish baking the rest of the cookie dough.
Buckwheat flour and toasted buckwheat groats are available at natural foods stores and well-stocked supermarkets. Toasted buckwheat (kasha) is some- times sold in the kosher aisle, or in the tea aisle at Asian markets. A good substitute for the toasted buckwheat is roasted cocoa nibs.