For the SPONGE:
½ cup (2 oz.) potato flour
2 cups (10 oz.) all-purpose flour
2 ¾ cups (22 fl. oz.) warm water
¼ cup (1 ½ oz.) stone ground rye flour
1 teaspoon instant yeast
For the DOUGH:
3 1/8 cups (14 oz.) King Arthur Bread Flour
2 teaspoon kosher salt
For the POTATO GARNISH:
2 small new potatoes, peeled
Oil as needed
To make the sponge, combine the potato flour, all-purpose flour, warm water, rye flour and yeast in a deep bowl. Stir with a spatula or sturdy whisk to combine. Cover and set aside for one hour. It will bubble up actively.
To make the dough, scrape the sponge into the bowl of a mixer fitted with the dough hook. Add the bread flour and salt. Knead on low speed until the flour is moistened. Scrape the bowl and increase the speed to medium. Knead the dough until it is smooth and elastic for 5 more minutes. It will be quite moist and somewhat sticky.
Using moistened hands, gather the dough into a ball. Scoop it into a plastic container. Cover and allow the dough to ferment and rise for 1 ½ to 2 hours.
While the dough ferments, make the potato garnish. Cut the peeled potatoes into paper-thin slices using a mandolin or sharp knife. Put the slices into a bowl of cold water. Blanch the potato slices in boiling salted water for 2 minutes, just until they are flexible and softened. Drain the slices of cooked potato in a strainer then place them in a single layer on paper towels to dry.
Form the dough into a smooth ball. Sprinkle the inside of the Emile Henry Bread Pot with flour. Place the dough into the pot.
Lightly brush each slice of potato with oil. Lay the slices of the potato on top of the dough overlapping in a decorative pattern. Cover and let the dough proof until it fills the bowl and is visibly risen, for approximately 30 to 40 minutes.
Preheat the oven to 475°F.
Uncover the pot. Using a serrated knife or baker’s lame, slash the exposed surface of the dough horizontally in several places. Replace the cover. Bake for 45 to 50 minutes until the dough is golden brown, fully risen and crisp. Remove the lid and bake for 5 additional minutes to darken the top crust.
Cool the bread completely on a wire rack before slicing.