To make the dough, combine the yeast and warm milk in a medium-size mixing bowl and stir to dissolve the yeast. Add 1 cup of the flour and mix to blend well. Add the vanilla pulp (discard the bean) and let stand at room temperature in a warm, draft-free place for about 2 hours to allow fermentation.
Put 2 cups of the remaining flour in a large mixing bowl. Add 4 of the eggs one at a time, beating well with a wooden spoon after each addition. The dough will be sticky, thick, and spongy. Add the warm water, 3 tablespoons of the granulated sugar, and the salt and mix well, beating vigorously. Add the butter and work it into the dough with your hands until it is all incorporated. Add 2 more of the eggs and mix well. Add the remaining 2 cups flour and blend into the dough, breaking up any lumps with your fingers. Add the yeast mixture and using your hands, knead and fold it into the dough. Continue kneading and folding until everything is well mixed, about 5 minutes. The dough will be sticky and moist. Cover with a clean cloth and let rise in a warm, draft-free place until doubled in size, about 2 hours.
With your fingers, lightly punch down the dough. Cover and let rise again in a warm, draft-free place until doubled in size again, about 1 hour.
Remove the dough from the bowl and divide into two equal balls. Refrigerate one portion while working with the other.
Lightly dust the work surface with flour and roll out the dough into a rectangle about 14 inches long, 10 inches wide, and 1/4 inch thick. In a small bowl, lightly beat the remaining egg. With a pastry brush, brush the edges of the dough with the beaten egg. In another small bowl, combine the remaining 1 cup granulated sugar and the cinnamon. Sprinkle half of the cinnamon sugar over three fourths of the dough. Roll the dough up tightly to form a log, starting from the long side. Wrap it in plastic wrap and freeze for 30 minutes. Repeat the process with the remaining dough.
For the topping, combine the butter, brown sugar, and cinnamon in a bowl and blend well. Spread the mixture over the bottom of two 10 X 2-inch round cake pans. Sprinkle both evenly with the pecans.
Remove the dough logs from the freezer and, with a sharp knife, cut crosswise into 1 1/2-inch-thick slices. Lay the slices on top of the butter-and-pecan mixture, about 1/2 inch apart. Let the buns rise in a warm, draft-free place until doubled in size, about 1 1/2 hours.
Preheat the oven to 400°F.
Bake until golden brown, about 35 minutes. Remove from the oven, let cool for about 5 minutes, and then flip onto a large serving platter and serve.
Yield: 18 buns