In a small bowl combine the yeast, warm water, and sugar. Mix briefly to combine and let stand until foamy, about 5 minutes or so.
To a large bowl add 4 ½ cups of flour, sugar, and salt. Stir to combine. Work the butter into the flour mixture with your hands or wooden spoon until mostly combined. Add the eggs and the yeast mixture. Stir the dough with a wooden spoon until a very sticky dough comes together.
Turn the dough onto a lightly floured surface and knead the dough, adding the remaining ½ cup of flour gradually until the dough becomes smooth and elastic. If the dough becomes too sticky to handle, pour about ¼ cup of flour on the counter next to the ball of dough and periodically dust your hands with the flour and continue kneading. Don’t be tempted to add too much additional flour. This dough will remain pretty soft so don’t expect for a ball of firm dough. It’s not going to happen. The most you will get is a less sticky dough.
Form the dough into a ball and transfer it to a lightly oiled bowl. Flip once or twice to coat and cover the bowl with a damp kitchen towel. Allow the dough rise in a warm spot until it doubles in bulk, about 2 hours.
Butter two 9x5-inch loaf pans.
Turn the dough out to a lightly floured surface. Divide it in half. Press down one piece of dough at a time and form into a rectangle. Begin to form a loaf by rolling the dough from the short end, much like forming a jelly roll. Pinch the seams and place the loaves seam side down in the pans. Cover the loaf pans with a damp towel and let it rise in a warm place until doubled in size, about 1 hour.
Preheat the oven 350° Fahrenheit.
Uncover the risen loaves and brush them gently with beaten egg. Cover the loaves loosely with aluminum foil. Place in the oven and bake for 15 minutes. Remove the aluminum foil and continue baking for another 15-20 minutes until the loaves are a nice golden brown, the bottom sounds hollow, and the internal temperature of the loaves register at least 190° Fahrenheit.
Remove from the oven and allow to cool for 3-5 minutes. Remove the loaves from the pans, place in a wire rack and allow the loaves to cool completely before slicing.