Place 1 cup plus 2 tablespoons of margarine in a large mixing bowl. Sift in the flour. Cut in margarine with 2 knives or pastry blender until mixture resembles coarse crumbs. Whisk cold water and egg together in a bowl. Whisk in lemon juice. Stir into flour mixture until dough is moistened. Turn dough out onto a lightly floured surface and knead briefly until it is smooth.
Roll the dough into a long log. Divide dough into 9 equal parts, roll each part into a small ball and chill for at least 1 hour, or overnight.
Preheat oven to 350 degrees F (175 degrees C).
Dust a large piece of parchment with flour. Take one of the dough balls, dust with flour, and place on prepared baking sheet. Roll into a thin and rough 8-inch circle. Prick with a fork all over. Transfer dough circle and the parchment paper onto a baking sheet.
Bake in the preheated oven until golden brown, about 10 to 15 minutes. Repeat with the remaining balls of dough.
Once pastry circles are baked, remove each one from oven. Place a large plate on top and cut around the plate with a sharp knife, so all the dough circles are the exact same size. Save the trimmings for later.
Place 3/4 cups plus 2 tablespoons butter in a large bowl; beat with an electric mixer until smooth and creamy. Beat in the condensed milk until smooth.
To assemble the cake, place one pastry circle on a serving plate and cover with 1 tablespoon of the butter filling. Sprinkle with walnuts and cover with the next pastry circle. Repeat till all of the pastry circles have been used, spreading filling on the top of the final pastry circle, but no walnuts.
Crush the reserved trimmings into crumbs. Sprinkle evenly to cover the top and sides of the cake.
For best results, chill Napoleon Torte in the fridge for 8 hours before serving.