- Mix together yeast, sugar, and salt in a large bowl.
- Pour in milk, stir until dissolved.
- Whisk in 1 cup of flour, cover, and let rise in a warm place until doubled, about 15 minutes.
- Stir in egg, egg yolk, and vanilla extract.
- Knead remaining 2 cups flour and butter into yeast mixture, adding each alternately a little at a time.
- Kneed until smooth and elastic, about 15 minutes.
- Place dough in a large bowl, cover, and let rise until doubled, about 1 hour.
- Simmer poppy seeds in a medium pot full of water until soft, about 40 minutes.
- Drain and puree in a food processor, about 4 minutes.
- Return poppy seed puree to same saucepan.
- Add sugar, butter, raisins, almonds, vanilla extract, and honey.
- Cook, stirring, over medium-low heat for 15 minutes.
- Set aside to cool.
- To cook: preheat oven to 350°F.
- Roll out dough to a 16" x 12" rectangle.
- Whisk egg white in a bowl into stiff peaks, fold into the poppy seed filling.
- Spread over dough, leaving a 1" border all around.
- Fold dough lengthwise in thirds to form a long log.
- Pinch ends to seal.
- Place cake on nonstick baking sheet, brush with beaten egg white, and bake until it sounds hollow when tapped, about 50 minutes.
- Cool before serving.