Add 2 1/4 teaspoons active dry yeast and 2 tablespoons sugar to 1/2 cup warm water and stir to combine. Let stand 5 minutes or until yeast is frothy.
Combine 3 cups of the flour and the 1 teaspoon salt in the bowl of a stand mixer fitted with the dough hook. Add the 1 cup ricotta cheese, 1 egg and 1/2 cup butter and mix until just combined. With the mixer on low, gradually add the yeast mixture.
Continue to mix on medium-low speed until the dough comes together. Add the last 1/2 cup of flour a tablespoon at a time until the dough is shaggy and just pulls away from the side of the bowl. The dough should be quite soft.
Transfer the dough to a lightly greased bowl and cover with a clean towel. Allow to rise until doubled, 1 1/2 to 2 hours.
Preheat the oven to 375 degrees 30 minutes before baking the bread. Before preheating, place a cast iron skillet or baking pan on the lowest rack (or on the floor of the oven). Grease a 9x5 inch loaf pan; set aside.
Turn the dough onto a lightly floured surface and shape into a loaf. Place in the prepared pan. Cover loosely and allow to rise until doubled, 40-60 minutes.
With a sharp knife, make a 1/2 inch deep slash down the center of the loaf. Place the pan in the oven and quickly toss 1/2 cup of ice cubes into the pan beneath and close the door.
Bake for about 45 minutes, or until a knife inserted in the center comes out clean. Cover with foil part-way through baking, if needed, to avoid over browning.
Remove the bread from the oven and cool on a wire rack for 5-10 minutes before removing from the pan to cool completely.