In a large mixing bowl combine 5 cups flour, 3/4 cup sugar, 1 teaspoon salt and 2 packages dry yeast. Heat 1 1/2 cups water to boiling. Melt 1/2 stick butter in water. Combine with 2 well beaten eggs. Add liquid to dry ingredients. Mix only until all dry ingredients are moistened and a soft dough results.
Turn dough onto lightly floured surface and knead firmly for 10 minutes. Place dough in a lightly greased bowl. Cover well with a damp cloth and place in a warm place. Allow to rise 1 hour or until doubled. "Punch down" - knead dough lightly to expel bubbles. Divide in 2. Separate each half into 3 sections. Roll each section between hands to form long rolls.
Place each section on a greased cookie sheet, braiding the 3 sections into a loaf. Repeat with other half. Both loaves will fit on one cookie sheet. Allow to rise until doubled in size. Brush with beaten egg. (Sprinkle with poppy seed, if desired.) Bake at 350 degrees for 18 to 20 minutes. Remove and allow to cool on rack. Eat warm.