Thumbprint cookies are traditionally flavored with vanilla and filled with fruit jam, but these are chocolate cookies stuffed with more chocolate! They will be a welcome treat on your holiday cookie platter, and they are a perfect hostess gift.
- 2 ounces unsweetened chocolate, finely chopped
- 2 cups unbleached all-purpose flour
- ¼ teaspoon salt
- ½ pound (2 sticks) salted butter, at room temperature
- ½ cup granulated sugar
- 1/3 cup firmly packed dark brown sugar
- 2 large eggs, separated, at room temperature
- 1 teaspoon pure vanilla extract
- 3 cups finely chopped pecans
- 8 ounces semisweet chocolate, finely chopped
- 2 teaspoons vegetable oil
To make the cookies: Heat the chocolate in a microwave-safe medium bowl on Medium (50% power), stirring at 30-second intervals, until fully melted and smooth. Let stand, stirring occasionally, until tepid, but still fluid.
In a medium bowl, whisk together the flour and salt. In a large bowl, beat the butter,granulated sugar, and brown sugar with an electric mixer set on high speed until combined, about 1 minute. One at a time, beat in the egg yolks, followed by the tepid chocolate and the vanilla. With the mixer on low speed, mix in the flour mixture, just until combined. Divide the dough in half and shape each half into a thick disk. Wrap in plastic wrap and refrigerate until chilled, about 2 hours.
Position the oven racks in the top third and center of the oven and preheat the oven to 350°F. Line 2 large rimmed baking sheets with parchment paper or silicone baking mats.
Using a heaping teaspoon for each, roll the dough into 78 marble-sized balls, putting them in a baking pan or platter. (If you wish, you can cover the balls with plastic wrap and refrigerate for up to 2 days.) Beat the egg whites in a small bowl until foamy. One at a time, dip each ball in the whites, roll in the pecans, and arrange 1 ½ inches apart on the prepared baking sheets. Refrigerate the remaining balls until ready to bake. Using your thumb (or, if you have long fingernails, the end of a wooden spoon), press an indentation into the center of each cookie.
Bake, rotating the positions of the sheets from top to bottom and front to back halfway through baking, until the edges of the cookies look set, about 10 minutes. Remove the baking sheets from the oven, and, using your thumb (or the end of the wooden spoon), reform the center indentation in each cookie. Return to the oven and continue baking until the cookies are crisp, about 10 minutes more. Let cool on the baking sheets for 5 minutes. Transfer to wire cooling racks and let cool completely. Repeat with the remaining balls, egg whites, and pecans, on cooled baking sheets.
To make the filling: Heat the chocolate and oil together in a microwave-safe bowl on Medium (50% power), stirring at 30-second intervals, until fully melted and smooth. Let stand, stirring occasionally, until tepid but still fluid.
Using a teaspoon, fill the indentations with the chocolate mixture. Let stand until the chocolate sets (you can refrigerate them to speed things up).