Boil condensed milk in can for 40-60 minutes. Let cool.
Shred margarine with flour, add citric acid in water and salt, knead puff pastry. Roll it into 2 inch (5-6 cm) bar and cut into 8 cakes. Wrap them into parchment paper and put in the deep-freezer for an hour. Then roll them in ¼ inch (0.3-0.5 cm) thick cakes and bake for 5-8 minutes over 390oF (200oC). Cool.
For cream, keep butter at room temperature, beat, adding boiled condensed milk little by little until the paste is fluffy. Add some nuts and mix carefully.
Smoothen the cakes edges with a knife. Shred the cut-offs and blend with the rest of nuts.
Put the cakes one on another, creaming apiece. Spread the cream on the top, sprinkle with the nut-and-crumb mixture and powdered sugar.
