If you can, make these ahead of time—the flavor improves immensely after 2 days.
Preheat the oven to 350°F. Grease a 13 × 9 × 2-inch baking pan and line with parchment paper so it extends over the 2 long sides.
Whisk together in a medium bowl:
Beat in a large bowl until thick and pale:
Add the flour mixture to the batter in 2 parts, alternating with:
Stir in:
Spread the batter evenly into the prepared pan. Bake until set, about 20 minutes. Place the pan on a rack. While still warm, spread evenly with:
Let stand until completely cool and the glaze is set, then cut into bars.