Combine flour, yeast, sugar, vanilla sugar, butter, water, eggs, egg yolks, and salt in a large bowl. Turn out on floured board and knead 5 minutes, adding up to 1 cup of flour if the dough is sticky. Allow to rise in a large bowl covered with plastic wrap for 1 1/2 hours.

Crumble butter with flour and sugar in a small bowl, using fingertips.

In a small bowl, combine butter, chocolate pudding, egg, water, sugar, and cocoa. Use an eighth of this recipe for each section of dough.

Spray 4 (10-inch) loaf pans with nonstick cooking spray. Divide dough into 8 pieces. Using a rolling pin, roll each piece into a 1/2-inch-thick rectangle, the length of the loaf pan. Spread filling onto each rectangle, within 1 inch of borders. Roll from long side, like a jellyroll. Twist 2 rolls around each other and place a twist in each pan. Using all the crumbs, sprinkle a quarter of crumb topping on each babka. Let rise for 30 minutes.

Preheat the oven to 350°F.

Bake for 30 minutes. Cool for 15 minutes in pan, then remove and cool completely on wire rack.