Combine the yeast and 2 cups warm water in a mixing bowl and stir to dissolve. Add the butter, sugar and salt. Use a wooden spoon to stir in one-third of the flour until smooth. Add another third of the flour and stir, then turn it out onto a floured board to knead. Knead it over 15 minutes, adding the rest of the flour as you knead. Don’t let it get dry too fast; it should stay sticky. Put the dough in a buttered bowl and cover with plastic wrap. Let it rise for 1 hour.
Knead the dough another 5 minutes, place it back in the bowl and let it rise another hour.
Butter 2 loaf pans. Shape the dough into 2 loaves and transfer them to the prepared pans. Cover and let rise for 45 minutes.