Fig 'n' Flax Thumbprint Cookies

Preheat oven to 350 degrees F. Line a large baking sheet with parchment paper or a nonstick baking mat.

Beat butter and 1/4 cup brown sugar in a medium bowl with an electric mixer on medium-high speed until creamy. Add egg yolk and vanilla and beat until combined.

Whisk whole-wheat flour, all-purpose flour, 2 tablespoons ground flaxseeds, cream of tartar, cinnamon, nutmeg and salt in another bowl. Slowly add the flour mixture to the batter and beat on low until just combined, scraping down the sides as needed.

Place the egg white in a small bowl. Combine the remaining 1/4 cup each brown sugar and ground flaxseeds in a shallow dish. Roll slightly rounded teaspoons of dough into balls. Dip one ball at a time into the egg white and then roll in the sugar mixture. Place 2 inches apart on the prepared baking sheet. Press your thumb (or index finger) into the middle of each cookie and spoon enough preserves (about 1/4 teaspoon) into the well to fill it.

Bake the cookies in batches until set, 15 to 17 minutes. Transfer to a wire rack to cool.