"This traditional Polish cake is rich with poppy seeds and usually served for special occasions like Christmas and Easter, but it's wonderful any time. A short crust base is topped with a poppy seed mixture, then glazed. Unique, delicious, and quite easy to do!"
Place poppy seeds in a small pot, cover with boiling water and set aside for 24 hours.
Line a colander with a cheesecloth and spoon in the poppy seeds. Allow to drain for several hours. Once drained, transfer to a food processor and process until fine.
Combine 1 1/2 cups flour, 3/4 cup margarine, 1/3 cup sugar, 1 egg, and baking powder in a large bowl and knead into a smooth dough.
Preheat oven to 350 degrees F (175 degrees C). Grease a deep quarter sheet pan (9x13-inches) and line with parchment paper.
Roll out dough on a slightly floured surface and place in the prepared sheet pan.
Combine egg yolks, 9 tablespoons margarine, and 1 cup sugar in a large bowl; beat with an electric mixer until light and fluffy. Beat in drained poppy seeds gradually. Add apples, honey, breadcrumbs, walnuts, and raisins and mix well.
Beat egg whites in a glass, metal, or ceramic bowl until stiff peaks form. Lift your beater or whisk straight up: the egg whites will form sharp peaks. Fold egg whites into poppy seed mixture; spread over base in sheet pan.
Bake in the preheated oven for 1 hour until cake is set; transfer to a wire rack to cool.
Mix enough boiling water with confectioner's sugar to form a smooth icing. Spread generously over cooled cake.