First step to make schiacciata is to make the poolish or pre-fermented 1st dough. Which needs 12 hours to ferment at room temp. Apre-fermented dough helps with the doughs extensibility and flavor development, similar but wetter than a biga
So in a large bowl, big enough for all the contents of the dough and using a scale measure out 1 gram of active dry yeast, 250 grams of bread flour, mix it all together and add 250 grams of warm water around 90 degrees.
Using a spatula, mix together until there's no dry lumps and it's well combined, I like using a spatula, and once the mixture is homogeneous, very wet dough, then cover with plastic wrap and let it sit at room temperature for 12 hours or overnight.
After 12 hours, you've got Poolish, the preferred first dough or starter which will help us achieve better extensibility and flavor in our Schiacciata.
Schiacciata Dough:
The poolish should have risen by about double overnight and is bubbly and jiggly. There should have about 500 grams of poolish, So again, using a scale, add another 500 of flour but this time All Purpose flour. Then add another 250 grams of warm water, and then 6 grams of salt. Then just like before, using a spatula, combine the mixture and hydrate the dough and once the dough becomes workable, knead it together with your hand until all the flour gets fully hydrated. Then add some more olive oil, knead it into the dough, once a rough ball is formed, place it in the bowl, drizzle a bit more olive oil and then cover with plastic and allow it to rise for 2 hours, stretching and folding the dough every 30 minutes.
Stretch and Fold:
After 30 minutes of rest, this is the first of about 3 periods of stretching and folding. It’s essentially the method for kneading a dough that has too high a hydration level to knead the normal way. But stretching and folding builds structure and gluten just like kneading as long as we alternate between stretching and folding and resting. because like we know with pasta dough, not only does kneading dough aid in the development of gluten but so does time and resting. You can stretch and fold a few ways. You can just pick the ball up and stretch, fold, rotate and repeat. Or you can place the ball in the bowl and just pull and stretch, fold it onto itself, rotate the bowl and repeat. And you don’t need to go crazy, just a few folds each time goes a long way. Get it back into the bowl, cover and rest again for 30 minutes. Repeat this every 30 minutes until the dough has doubled in size and is a smooth ball of dough.
Rest Overnight:
After about 2 hours of rising in the bowl, the dough should have at least doubled in size. Prepare a large sheet tray by drizzling a bit of olive oil on the bottom and spreading it out with your hand. Then slide the dough, seam side down, onto the sheet tray. Drizzle a bit more olive oil on top of the dough and with your finger tips, press down to squash, or schiacciare (the Italian word for squash) to create these little dimples and to gently spread the dough out. I’ll spread it out about half way, then drizzle a tough more olive oil on top and then wrap with plastic and place in the fridge overnight.
The next day, 2 hours before you’re ready to bake the bread, take the sheet tray out, press down with your fingertips to spread the dough out even further and thinner. Once the dough is spread out evenly and fills up most of the sheet tray, cover it back up with plastic wrap and allow it to rise one more time for 2 hours.
Pistachio Cream:
In a food processor, add in one 6 oz package of shelled, roasted and salted pistachios. Pulse until the pistachios have the texture of coarse panko breadcrumbs. Then pull out 2 tablespoons and reserve for later. Then add in about a cup of parmigiano cheese and then stream in olive oil until the mixture becomes thick, creamy and spreadable. Taste and adjust with salt if needed, then set aside.
Stracciatella:
Stracciatella means “little shreds” and it is a way for cheese makers to use scraps of mozzarella. It is also the filling of burrata. So if you can’t find Stracciatella itself, you can always get a couple balls of burrata, add the filling to a bowl and then shred up the mozzarella shell and mix it all together, season with a touch of salt and you’ve got Stracciatella. Set aside.
Bake the Schiacciata:
Preheat the oven to 450F degrees.
After two hours of rising, uncover the dough, drizzle with more olive oil, brush it all over the top for the dough. Sprinkle some flakey sea salt, then place in the preheated oven for about 20 minutes, rotating half way. Once lightly golden brown, remove from the oven and let cool for 5-10 minutes until cool enough to handle.
Assemble the Sandwich:
Once the sandwich is cool enough to touch, cut the bread in half lengthwise, then cut a square piece roughly the size of your hand. Slice it in half, open it up and on the bottom half, spread the pistachio cream, the stracciatella, and the pistachio crumbs. Then drape the mortadella beautifully on top, making sure you don’t lay them flat, but rather folding into airy bundles. Then sprinkle a bit more crumbled pistachio on top. Close it up and enjoy. You can now enjoy the world’s most famous sandwich, no line.