Place the yeast, a pinch of flour and a pinch of sugar in a small mixing bowl. Pour lukewarm water over it. Stir until they dissolved. Let it rise in a warm, draft-free place until frothy. About 10 minutes. (If it doesn’t get frothy, it means that the yeast is no longer active and you will have to start again with fresh yeast.) 

In the bowl of a heavy-duty electric mixer, fitted with the dough hook, mix all other dough ingredients.

Knead the dough until it forms a rough ball, clean the sides of the bowl. (in an upright KitchernAid speed 2 for 8-10 minutes).
Turn the dough out onto a floured surface. Knead the dough, adding flour or water if necessary to prevent the dough from sticking to your hands and to the table, until the dough is smooth and soft.

Place in a deep bowl, cover with a kitchen towel and set the dough to rise in a warm, draft-free place until doubled in bulk, 1-1½ hours, depending on the environment.

Punch the dough down to deflate it, then let it rise one more time. Depending on the environment, this second raisings can take from 20 minutes to 45 minutes.

Turn the dough out onto the floured surface. Cut the dough into five equal parts and each part to 3 balls (15 in all). Knead each into a ball.

Combine filling ingredients. To a smooth paste.

Roll out each ball separately, spread with the filling paste. Roll to a log.

Braid every 3 logs together, place in a well-buttered loaf pan or Bundt cake pan and let rise again.

Preheat oven to 350°F. Bake about 35 minutes. 

Mix yolk with a teaspoon of water.

When done, spread yolk and sprinkle with vanilla sugar on top.​