Make the Poolish

1. In a medium bowl, mix together flour, dry yeast, sugar, and water until a sticky dough is obtained. Add more water if necessary to achieve this.
2. Cover loosely with a plastic film and leave to rise for about 2 hours. The poolish should be somewhat bubbly and have doubled in size.

Make the dough

1. The dough can be mixed by hand or in a machine. Mix together the flours, water (more or less as required), oil and poolish. The dough will be sticky.
2. Let the dough rest for 20 minutes. Sprinkle the salt over the dough and dissolve with a bit of water. Work the salt into the dough and knead until it is soft, very pliable and smooth.
3. Shape into a round and place in a bowl. Cover the bowl loosely and leave it to rise till double in volume. About 2 hours.
4. Alternately, allow the dough to rest for 1 hour, cover tightly, and place in the refrigerator overnight.

Cook the onions

1. While the dough is rising, get the toppings ready. Heat the oil in a pan and add the sliced onions. Sprinkle a little salt (if desired) and cook the onions on low to medium heat until they turn translucent and soft. Do not brown or caramelize them. If they turn too dry, sprinkle a little water while cooking them. Take the pan off heat and let them cool to room temperature.

Prepare the breadcrumb mixture

1. Run the bread slices (with or without crusts) in a food processor to make the crumbs. Put the breadcrumbs in a bowl.
2. Mix together with the oil, salt, red chili flakes (or crushed pepper) chopped scallions/spring onions, oregano and grated cheese. The texture should be of loose but moist crumbs.

Assemble the Sfincione

1. If you allowed the dough to cold ferment in the refrigerator, remove it and let it warm up to room temperature before assembling the pie.
2. Gently knead to deflate the dough. Press it out into a roughly 9-inch circle (or oval) using your fingers. If the dough feels sticky, oil your fingers lightly.
3. Place in the prepared pan or pie dish. Let the dough rise again, for about an hour till almost double in thickness and quite puffy.
4. Top with anchovy (if using), then the cooked onions. Next comes the Ricotta and Tuma/ Primo Sale cheeses. Make sure to cover the surface of the dough evenly. Finish layering by spreading the breadcrumb mixture on the top.

Bake the Sfincione

1. Place the assembled pie in a preheated 250C (480F) oven on the bottom shelf and bake for about 10 to 12 minutes. The underneath of the bread should become golden and crisp.
2. Move the pan to the middle shelf of the oven and bake for another 10 minutes or so, until it is crisp and golden brown on the top as well.
3. Remove from the oven and let cool. Slice and serve.
4. Leftovers can be refrigerated for up to 2 days.
5. Reheat leftovers at 325 degrees F in foil for 10 to 15 minutes.