Many a copy of Joy has been sold on the strength of this recipe.
Preheat the oven to 350°F. Grease a 9-inch square baking pan and line with parchment paper so it extends over 2 sides.
Beat in a medium bowl until well blended:
Stir in until well blended and smooth:
Press the dough evenly into the baking pan. Bake for 10 minutes and remove from the oven (leave the oven on). Meanwhile, beat in a medium bowl until well combined:
Stir in:
Spread the mixture evenly over the hot baked crust. Return to the oven and bake until the top is firm and golden brown and a toothpick inserted in the center comes out slightly wet, 20 to 25 minutes. Set the pan on a rack. If desired, while still warm, spread evenly with:
Let stand until completely cool and the glaze is set before cutting into bars.