For the nut filling: Mince the ingredients. Combine all of the ingredients listed under "nut filling" in a bowl, and knead them until they come together into a ball. Adjust the amount of water depending on the consistency.
For the cookie dough: Put the margarine and sugar into a bowl and cream together. When the mixture turns white, add the beaten egg a little at a time, in several batches.
Add the cake flour to the mixture from Step 2, then briskly mix with a rubber spatula. Roll the dough out to a 5 mm thickness. Make two sheets of dough to fit the pound cake mold.
Line the mold with plastic wrap or parchment paper.
Fill the mold first with a layer of dough, then a layer of nut filling, then a layer of dough, making sure to press firmly after each layer to fill in any gaps. Press down on the top for good measure.
Chill in the refrigerator for about 30 minutes. Preheat the oven to 180
Remove the mold from the refrigerator and release the cookie and lining from the mold. Brush an egg wash on top of the cookie dough.
Bake in preheated oven for about 25-30 minutes. Cool, then cut and serve.
I made high-fiber cookies with 40 g cake flour, 10 g whole wheat flour, 20 g okara, 20 g prunes, and 10 g orange peel. They're delightful.