Brown-Sugar Chocolate-Chunk Shortbread

1. Beat together butter, sugars, and salt on medium speed until creamy and combined, 2 minutes. Add vanilla. Reduce speed to low, add flour, and beat to combine. Beat in chocolate. Divide dough into two pieces, each about 1 pound. Roll into logs (each about 8 1/2 inches long and 1 3/4 inches in diameter).

2. Wrap logs in plastic and refrigerate until firm, about 2 hours. Dough can be made to this point, well wrapped, and frozen for up to 1 month. (It can also be sliced and re-formed into logs before freezing; see cook's note.)

3. Remove from refrigerator or freezer (if frozen, let stand 10 minutes to soften). Brush with egg white and roll in sanding sugar to coat. Use a serrated knife and a back-and-forth motion to cut logs into 1/2-inch-thick slices (if any crack around larger chunks of chocolate, just press back together).

4. Preheat oven to 325°F. Place cookies on parchment-lined baking sheets and bake until golden on edges, 16 to 18 minutes. Let cool on pans on wire racks 10 minutes, then transfer to racks and let cool completely, about 45 minutes. Store in an airtight container at room temperature up to 3 days, or freeze up to 1 month.

Cook's Notes

Slicing a chilled log and re-forming it before freezing lets recipients chip off and bake just a few at a time.