Slowly add four more cups of flour to the mixture (for a total of 7 cups). Mix well. Knead until elastic (about 10 minutes). Let rise for 40 minutes in a draft-free place. Punch down and knead for about 5 minutes. Form into 2 to 4 braided loaves. Let rise for another 30 minutes. Brush with egg yoke glaze (1 egg & 1 tsp. of water). Sprinkle with sesame seeds or poppy seeds (optional). Bake at 350 degrees Farenheit for 20 to 25 minutes. If you thump it gently and it has a hollow sound, it is done.