1. Cut the Focaccia to the desired size and slice it in half.
2. Toast it in olive oil in a pan.
3. Cut and rinse the vegetables.
4. Stem the peperoncini peppers.
5. Cut the mozzarella into suitable pieces.
6. Chop the pistachios. Spread aioli on both sides of the Focaccia.
7. Start by sprinkling pistachios, then layer with mozzarella, tomatoes, and folded pieces of Mortadella.
8. Place Peperoncini peppers in between to add some vibrancy, edge, and acidity to the sandwich.
9. Finish by drizzling olive oil over the filling, then place the top piece of Focaccia on.

- Serve immediately, and enjoy your delicious Focaccia Sandwich with Mortadella and Peperoncini!

Enjoy your meal!