Mandelbrot (no relation to famous mathematician Benoit Mandelbrot or the Mandelbrot Set) are Jewish Almond Cookies (from German, Mandel=Almond, Brot=Bread). Something like biscotti, but even better. Great with coffee or hot chocolate. Also a great homemade Christmas gift for that modern math professor with the bad sense of humor.
Into a bowl sift together the flour, baking powder, baking soda, and the salt. In the bowl of an electric mixer cream the butter with the sugar until the mixture is light and fluffy, add the eggs, 1 at a time, beating well after each addition, and beat in the zest, the vanilla, and the almond extract. Add the flour mixture and the almonds, beat the mixture on low speed until a dough is formed, and divide the dough into thirds.
Working on a large buttered and floured baking sheet, with floured hands for each piece of dough into a flattish log 10 inches long and 2 inches wide and arrange the logs at least 2" apart on the sheet. Bake the logs in the middle of a preheated 325 degree Farenheit oven for 30 minutes and let them cool on the baking sheet on a rack for 10 minutes. On a cutting board cut the logs crosswise on the diagonal into 3/4 inch slices, arrange the mandelbrot, cut sides down, on the baking sheet, and bake them in the 325 degree oven for 5 minutes on each side, or until they are pale golden. Transfer the mandelbrot to the rack to cool and store them in airtight containers.
Source: Gourmet, December 1992