PREP THE DOUGH
In a mixing bowl, whisk together flour and salt; set aside.
In separate small bowl, stir together water and yeast. Let sit for several minutes until foam forms on top.
Make a well in center of flour and add the yeast mixture; stir until combined. Add in the 3 tablespoons of olive oil and knead or mix with dough hook to combine.
If using an electric mixer, add hook attachment and knead for several minutes until dough pulls away from the sides and has an elastic texture. If kneading by hand, roll out on to floured surface and knead by hand for 10 minutes.
Add 4 teasopons of olive oil to large bowl. To that same bowl, add the dough and roll to coat dough in olive oil.
Cover top of dough with plastic wrap and then cover the top of the bowl with a clean towel.
Let rise for a least 90 minutes, until dough has doubled in size.
Once the dough has risen, punch dough down and divide into two even pieces. Cover the dough pieces with a clean towel while you prep the baking sheet and the filling.
If using right away, let rise another 30 minutes on counter covered while you prep the filling.. If using at a later date, place in greased plastic ziplock and refrigerate for up to 3 days.
FILLING
Fill a large sauce pan with water and add a teaspoon of salt. Bring to a boil. Add the broccoli and cook for about 5 minutes. Drain the broccoli.
In a large skillet, add the olive oil. Add the onion, stir until translucent. If using garlic, add in when the onions are translucent and stir to combine.
Add in the broccoli, tomatoes, and salt. Stir to combine. Cook until softened. Check the seasoning and add more salt to taste (if needed). Remove the pan from the heat and let it cool down while you prep the baking sheet with the dough.
ASSEMBLE THE SCIACCIATA
When ready to make the sciaciatta, heat oven to 425 degrees F.
Line a large baking sheet with parchment paper and drizzle on about a tablespoon of olive oil. Spread the olive oil all around the parchment paper.
Roll out both pieces of dough on a lightly floured clean work surface.
Place the first piece of dough on the bottom of the baking sheet. Stretch it out to fit the perimeter of the baking sheet. It’s fine if some of the dough is hanging over (you’ll be folding that with the top pieces to seal the edges of the scacciata).
Spoon the broccoli filling over the dough. Add the olives on top of the filling.
Place the second piece of dough over the filling, stretching it to reach the edge of the pan.
Pinch the two doughs together to seal in the filling, rolling the dough pieces to form a crust around the perimeter of the scacciata.
Poke the surface of the top layer with a fork every few inches.
Brush the top of the dough with some olive oil mixed with a little bit of water (you could also brush it with a beaten egg).
Bake for 25-30 minutes or until the top gets golden brown.
Let it rest for 10 minutes before slicing.