Proof the yeast in the lukewarm water in a large bowl. Add the sugar,
salt, butter, eggs, and 5 cups of the flour, a cup at a time. Beat
thoroughly with a wooden spoon or with the hands. Gradually add more
flour until the dough is very stiff. Turn the dough out on a board
sprinkled with flour. Knead until the dough is smooth and elastic,
approximately 10 minutes.
Place the dough in a very large buttered bowl, and turn to coat the
surface with butter. Cover and let rise in a warm, draft-free place
until doubled in bulk, about 1 1/2 to 2 hours.
Punch down dough and divide into six equal parts. Roll each portion
into a rope about 1 inch in diameter on a lightly floured board.
Braid three ropes together to make each of two loaves. Place the
braids 6 inches apart on a buttered baking sheet. Cover and let rise
in a warm place until almost double in bulk.
Brush the top of the loaves with the egg wash and sprinkle with poppy
seeds. Bake in a preheated oven at 400°F for 35 to 45 minutes, or
until the loaves sound hollow when tapped with the knuckles. Cool on
racks.
