Flourless Chocolate Walnut Cookies are easy-to-make cookies using simple ingredients and needs only one bowl. These fudgy, chewy chocolate walnut cookies are perfect for Passover or anytime you want gluten-free cookies!
Preheat the oven to 350 °F with two racks in the upper and lower thirds of the oven.
Spread the walnut halves on a half sheet baking pan lined with a Silpat silicone mat or parchment paper and toast them for about 9 minutes, until they are golden and fragrant. Let the walnut halves cool slightly, then transfer them to a work surface and coarsely chop.
Lower the oven temperature to 325 °F Line two half sheet baking pans with a Silpat slicone mat or parchment paper. If you're using parchment paper, spray it with baking spray so the cookies don't stick (see Recipe Notes).
Sift the powdered sugar and cocoa powder into a large bowl, then whisk to combine. Stir in the salt, then the chopped walnuts.
Mix in the egg whites and vanilla extract until the batter is just moistened. Don't over-mix the batter or it will stiffen (we’re not trying to whip these egg whites as we would for a meringue).
Scoop one tablespoon of the batter onto the baking sheets in evenly spaced mounds using a small cookie scoop. Let the batter dry at room temperature on their trays for 30 to 60 minutes before baking. It’s also fine to bake them right away, but they’ll not be quite so mounded. If you have the time, don't skip this step.
Bake the cookies for 14 to 16 minutes, until the tops are glossy and lightly cracked. Rotate the pans and swap their positions in the oven halfway through to ensure even baking.
After the cookies come out of the oven, lightly sprinkle them with sea salt flakes. These cookies need to firm up after baking, so let them cool completely on the pan. If you try to transfer them too soon, they can fall apart or leave half the cookie behind. Just be patient, and you'll have pretty, mounded cookies.
Storage instructions: Flourless Chocolate Walnut Cookies can be stored in an airtight container for up to 3 days. You can also freeze the cooled cookies in an airtight bag for 1 month.
Make-ahead instructions: Portion out the dough onto a baking pan, then freeze them until firm. Store in an airtight bag for up to 3 months. Bake them directly from the freezer (no need to thaw them first), just add about 1 to 2 minutes more of baking time.
Recipe Notes
If you prefer, you can replace the walnuts with 1½ cups (250 grams) of chocolate chips instead to make flourless chocolate chip cookies.If you strictly follow the rules of Passover, you may not use standard powdered sugar because it has cornstarch in it. If you don't have kosher for Passover powdered sugar, you can make your own: For the 3 cups of powdered sugar needed for this recipe, grind 2 cups (400 grams) granulated sugar and 1 tablespoon (10 grams) potato starch in an electric coffee or spice grinder until powdery. Measure and use as needed.Any type of cocoa powder (natural or Dutch process can be used). For a deeper chocolate flavor, use dark chocolate cocoa powder.Likewise, standard baking spray contains flour. If these cookies are for Passover, use one that follows the dietary rules, like one containing just vegetable oil.