Focaccia:

1. In a large bowl of a stand mixer whisk together the bread and whole wheat flours. Place the bowl on the stand mixer and fit it with a dough hook. 
2. Heat the water to 100°F (37℃). Whisk in the yeast until dissolved.  
3. Turn the mixer on low speed and pour in the yeast mixture. Mix for 10 minutes, scraping down the sides of the bowl occasionally to ensure all the flour is being hydrated. 
4. Add the salt and switch to medium-low speed and mix for an additional 10 minutes.
5. After 10 minutes, with the mixer running, pour in the olive oil and mix for an additional 3-5 minutes.
6. Use a bowl scraper to remove the dough, it will still be very sticky, to an un-floured work surface. Slap and fold the dough for about 2 minutes or until the dough starts to become smooth and holds together a bit more. To slap and fold simply pick the dough up and slap the bottom down and fold it over itself. Repeat this action by picking the dough up from the front and back or from the folded sides, rotating it a quarter turn and slapping and folding the dough again. This dough is extremely hydrated, so it will be very sticky; don’t worry if it is a little messy at first, as you continue to slap and fold you will get into a rhythm and the dough will stick less and less. 
7. Generously grease a 3-4 quart (2.8-3.7L) container with cooking spray. Drizzle olive oil over the greased container and then add the dough. Cover with a greased lid or plastic wrap and proof in the fridge for 48-72 hours. 
8. Grease a rimmed baking sheet with cooking spray and drizzle olive oil over that. Carefully remove the dough from the container and place it on the tray; its important you don’t deflate the dough during this process. Gently stretch the edges of the dough to so that they almost reach the edges of the baking sheet and are generally the same shape as the pan. Cover the baking sheet with another, inverted rimmed baking sheet. Wrap those in plastic wrap and let rise, at room temperature for 2-3 hours.  
9. Preheat the oven to 500-550℉ (260-288℃).
10. Unwrap the proofed dough and generously drizzle the top with olive oil. Dimple the dough with your fingertips if you would like; this is not required if you want to keep as much air in the dough as possible. 
11. Sprinkle the top with the za’atar and flakey sea salt; alternatively you can add any other spices, seasonings or toppings you’d like. 
12. Bake in the oven for 20-25 minutes or until the top of the dough is deeply golden brown and even begins to char in spots and the dough is fully cooked through. Let cool enough to handle before removing the bread to a cooling rack and continuing to cool. Slice while still a bit warm and serve.

Focaccia Sandwich:

1. Season the tomatoes on both sides with salt and set aside. 
2. Place the prosciutto slices in an even layer in a cold, non-stick pan. Heat over medium heat, flipping occasionally or until the prosciutto is golden brown and crispy. Remove to a plate and set aside. 
3. In a small bowl whisk together the mayo, pesto, lemon juice, salt and pepper to taste. 
4. Generously spread the pesto mayo on the top and bottom of the focaccia. Add half the lettuce to the bottom slice and top with the seasoned tomatoes, crispy prosciutto, fresh mozzarella, drizzle of olive oil, black pepper, salami, pickled peppers, and the rest of the lettuce. Add the top slice of focaccia to the top, cut in half and serve.