Mine may not be quite as pretty as the above but it was delicious! The original recipe makes two small loaves, so I froze half of the dough before the second rise. I've cooked the frozen one off since and it also turned out well. Don't forget to let it thaw AND do the second rise, though!
I didn't get a lot of good pictures of the process, so let's get straight to the recipe:
2 medium sized russet potatoes (about 8 oz.)
1 tbsp active dry yeast
1 tbsp sugar
2 tsp salt
1/2 cup water
4 1/2 cups bread flour or all purpose flour
1 cup Parmesan cheese, grated
1 egg, lightly beaten + 2 tbsp water
I used instant mashed potatoes by preparing them according to the package. I'm a big fan of not going to the store for a single ingredient and going with a substitution instead. One potato is about one serving of instant mashed potatoes, maybe a little more. Go figure. So, you'll need 2-3 servings of instant mashed potato.
Add the dry yeast and sugar and let stand for 10 minutes.
Add the salt, water and 3 cups of flour. Mix until smooth, adding more water if necessary.
Stir in the Parmesan cheese and gradually add in the rest of the flour by ¼ cup increments. I didn't have the full amount of Parmesan cheese but the bread turned out fine any how.
Turn the dough onto a floured surface and knead for 5-7 minutes, until dough is smooth and elastic. Add more water if necessary.
Drizzle some olive oil in the empty bowl and place the dough back into it. Cover with plastic wrap and let rise for 60 minutes, or until doubled in size.
Place the dough on a floured surface and deflate. Divide the loaves and freeze one.
Place the loaf on lightly oiled parchment paper,
Cover with a dish towel and let rise for 45 minutes.
Preheat the oven to 375ºF.
Stir together the egg and water and brush the wash over the loaf.
Bake for 30-40 minutes, until bread is a dark golden brown (internal temperature should read 195-200F).
Transfer to a rack to cool.
Here you can see how well the parchment paper works for a clean removal from the pan: