1. Preheat the oven to 325°f (165°c) gas 3 and grease an 8-inch-square cake pan.
2. In a large bowl, combine the flour and the rice or whole-wheat flour.
3. Cut the butter into 8 pieces and rub into the flour until the mixture looks like crumbs.
4. Stir in the sugar. Make a well in the center and drop in the 2 egg yolks.
5. Stir to combine some of the mixture with the yolks, then knead with your hand to make cookie dough. (If the mixture is too dry, add 1 or 2 teaspoons of cold water.)
6. Pat the dough into the prepared pan and bake for 20 minutes or until the surface looks dry.
7. Meanwhile, beat the egg white until stiff. Sift in the confectioners' sugar and stir to combine.
8. Stir in the almond extract. Spread this mixture on top of the shortbread and sprinkle with the sliced almonds.
9. Reduce the oven temperature to 300°f (150°c) gas 2.
10. Put in the shortcake and bake for 15 to 20 minutes or until the almonds are golden.
11. Let cool in the pan. Cut into 8 or 12 rectangles.