1 pound (4 stick) unsalted butter at room temperature
1 cup firmly packed light brown sugar
1 cup granulated sugar
2 teaspoons pure vanilla extract
1 teaspoon salt
3 3/4 cups unbleached all purpose flour
1 cup almond flour or very finely ground almonds
1 1/2 cups Blackberry, Raspberry, or other preserves or jam
1/2 cup chopped almonds, walnuts or other nut
confectioners sugar for dusting
Combine the butter and the sugars in a large bowl. Using an electric mixer set at medium low speed, beat until creamy. Add the vanilla and salt and beat until combined.
Beat the all-purpose and Almond flours into the butter mixture on low speed, just until a smooth, soft dough forms.
Spray a 9×13 inch baking pan with nonstick cooking spray and press one half of the dough evenly into the pan to form a bottom crust. Wrap the remaining dough in plastic wrap and refrigerate until very cold and very firm, at least 30 min.
Position a rack in the middle of the oven and preheat to 325 degrees.
Bake the bottom crust until it is firm and just beginning to turn pale brown around the edges about 15 to 20 minutes.
Remove the pan from the oven and spread the preserves evenly over the crust.
Crumble the remaining shortbread dough over the jam to form a pebbly, crumbled topping.
Sprinkle with the chopped almonds.
Return the pan to the oven and continue baking until topping is firm and crisp and lightly golden in color, about 20 to 25 minutes. Transfer to a wire rack and let cool to room temperature.
Use a sharp knife to cut bars evenly into 15 large squares. Remove the bars from the pan with a metal spatula and, if desired, cut in half on the diagonal to form 30 smaller triangular bars. Dust with confectioners’ sugar and serve.
The bars will keep, covered tightly, for about 1 week at room temperature, or in the freezer for up to 1 month.