To a medium bowl, add yeast, water, and granulated sugar. Stir to dissolve yeast and allow to stand for 5 minutes until foamy.
We are kneading dough by hand, so get ready. Add all the bread flour, about 4 cups of the all-purpose flour, and salt to a very large bowl. Rub in the butter with your hands until the butter almost disappears into the flour and the mixture has a slight sandy texture. Make a well in the center of flour and add the warm water and yeast mixture.
With a wooden spoon, stir the flour into the water until a sticky dough forms. Continue stirring with the wooden spoon, adding remaining dough about 1/4 cup at a time until a soft dough forms. Turn the dough to a lightly floured surface and knead the dough, adding more flour as needed (you may not use all the flour) until the dough is soft and tacky, but not sticky, about 10-15 minutes of active kneading.
Liberally butter a clean bowl (or the same bowl you used to mix dough). Place the dough inside the bowl and turn a few times to coat. Cover the dough with plastic wrap and place in a warm, draft-free place until the dough had doubled in size, about 1 hour.
Preheat the oven 375° Fahrenhet and grease two 9x5 inch load pans and set aside.
Turn the dough onto a clean, lightly floured surface. Gently press on the dough to remove air trapped during rising. Divide the dough in two. Working one piece at a time, gengtly pat and stretch the dough into a rough rectangle. Roll up the rectangle, one at a time, starting at the short end creating a tight cylinder. Pinch the ends and seam to seal the dough. Place the dough cylinders seam side down into greased loaf pans.
Cover the loaves loosely with plastic wrap and allow to rise until doubled in size, about 45 minutes. Remove plastic wrap from the loaves and brush each loaf gently with the melted butter.
Place the loaves in the oven and bake for 30-35 minutes, rotating about mid-way through for even baking, until the loaves are golden brown, and the internal temperature of the dough reads over 190° Fahrenheit in an instant-read thermometer.
Remove loaves from oven and immediately brush them with melted butter and sprinkle with Kosher salt. Allow the loaves to cool for about 5 minutes or so, then remove from pans and allow to cool completely.
Bread will last, well covered for about 4 days and about 1 month in the freezer.