Sprinkle yeast packet on top of your lukewarm water, stir a little bit and then let sit to activate.
*To scald you milk pour into a small saucepan and heat on medium heat until milk is just about to boil. Remove from heat and let cool.
Meantime in a large mixing bowl of a stand mixer with paddle attachment mix butter and sugar together. Add salt to the egg yolks and mix together, add to butter and sugar mixture. Scrape sides and mix to incorporate.
Add your activated yeast mixture and mix well. Add 4 cups of the flour alternately with scalded milk in batches until all is incorporated. Mix for about 5-7 minutes until dough is smooth.
Remove the paddle and scrape any of the dough that is stuck to it off. Place dough on a floured board or work surface. **It will be sticky but will become less sticky as you work in remaining 1 cup of flour.
Work the remaining 1 cup of flour into the dough until it is no longer sticky and there are no lumps. This should not take long. It should already be quite smooth from the mixer.
Cut the dough into two equal pieces. Cover one with plastic wrap and set aside.
Roll dough out on a floured surface to about a 10x12 rectangle.
Spread half of your poppy seed mixture almost to the edges of the dough.
Starting on the short edge roll the dough up to form a log.
Pinch the open ends of the dough on each side and tuck under the roll to seal and prevent filling from coming out.
Place Roll on a parchment lined baking sheet and repeat with second piece of dough.
Cover each Roll with a towel and place in a warm place. **I like to heat oven to about 100-170 Degrees F then turn off. Place the towel covered rolls in the warm oven for about 1 and half hours or until the dough has doubled in size.
Scramble the egg and water together to create egg wash.
Gently brush egg wash all over the top of the rolls with a pastry brush.**Careful not to pierce the bread or the filling may come out as it bakes.
Preheat oven to 350 Degrees F. Bake roll for 35 minutes.
Remove from oven and let cool before cutting.