TO MAKE THE DOUGH: Place the poppy seeds in a bowl, pour in enough boiling water to cover them by an inch and soak for 3 hours.
Pour the lukewarm water into a small, shallow bowl and sprinkle the yeast and 1/2 teaspoon of the sugar over it.
Let the yeast and sugar stand 2 or 3 minutes, then stir to dissolve them completely.
Set in a warm, draft-free spot, such as an unlighted oven, for 3 to 5 minutes, or until the mixture almost doubles in volume.
Transfer the yeast to a large mixing bowl.
Dissolve the 1/2 cup of sugar in the milk and then stir the milk into the yeast.
Beat in 3 cups of the sifted flour about 1/4 at a time.
Beat in the eggs one at a time and then the 1/4 pound butter broken into bits, and continue to beat until the dough can be gathered into a compact ball.
Transfer it to a lightly floured board and knead in the remaining cup of flour a few tablespoons at a time, pushing the dough down with the heels of your hands, pressing it forward and folding it back on itself.
Knead until all the flour is incorporated and the dough is stiff and quite dry.
Shape it into a rough ball, place it in a mixing bowl, and add enough COLD water to cover the dough by several inches.
In 10 to 15 minutes, the top of the ball of dough should rise above the surface of the water.
Remove the dough from the water and pat the surface as dry as you can with paper towels.
Return it to a floured board, punch it down, and knead again for 10 minutes, until the dough is smooth and elastic.
Shape the dough into a ball, place it in a lightly buttered bowl, and cover loosely with a kitchen towel.
Let the dough rise in a warm draft-free place for about 30 minutes, or until it doubles in bulk.
I put the dough in the oven with the pilot light on for warmth.
FOR THE FILLING: Meanwhile, for the filling, drain the poppy seeds and spread them out on paper towels to dry.
Then pulverize them, 1/2 cup or so at a time, in an electric blender or with a mortar and pestle and combine them with the almonds, raisins and lemon peel in a large bowl.
In a heavy saucepan, combine 3/4 cup of the milk and sugar and bring to a boil over moderate heat.
Reduce the heat to low.
With a whisk, beat the 2 Tablespoons of flour into the remaining 1/4 cup of milk, then slowly beat it into the simmering milk.
Again bring to a boil, whisking constantly, until the mixture is thick and smooth.
Pour it over the poppy-seed mixture and stir well.
Then beat in the egg yolk.
In a separate bowl, beat the egg white until it forms firm unwavering peaks on the beater when it is lifted out of the bowl.
With a rubber spatula, fold the egg white gently but thoroughly, into the poppy-seed filling.
TO MAKE THE ROLL: Coat the bottom and sides of two 5 by 10 by 2 1/2-inch loaf pans with 2 tablespoons of soft butter and set them aside.
Preheat the oven to 375 F.
When the dough has risen, punch it down and divide it into two equal pieces.
On a lightly floured surface, roll each half into a rectangle about 10 by 15 inches and a little less than 1/4 inch thick.
With a spatula, spread the filling evenly over the two rectangles to within 1/2 inch of their edges.
Dribble 4 Tablespoons of melted butter over each and then shape them as follows: First roll one long side to the center, jelly-roll fashion, then roll the opposite side to the center jelly-roll fashion.
Firmly holding both sides together, turn each cake over so that the seam is on the bottom when the cake is set in its pan.
Brush the tops with the egg and cream mixture and bake in the middle of the oven for 1 hour, or until the cakes are golden brown and crusty.
Cool in the pans for 5 minutes or so, then turn them out on a cake rack.
Cool completely before serving.
To make two 10-inch loaves The Cooking of Germany.