Preheat an oven. Cut the ciabatta in half lengthwise. I realize this is controversial, but feel free to scoop out some of the bread from the top side of bread to make room for the filling.
Place basil leaves, pistachios, lemon zest, fresh lemon juice, and garlic clove in the bowl of a food process. Process until finely chopped. Transfer to a bowl, then stir in grated Parmesan cheese. Add remaining olive oil if you want a thinner consistency, stirring until well mixed.
Place a generous layer of thinly sliced pistachio mortadella on the bottom piece of bread. Sprinkle the burrata cheese with flaky sea salt, then drizzle the sandwich with extra virgin olive oil (or truffle oil) and chopped pistachios. Spread a generous layer of pistachio pesto.
Place the top piece of bread on top. If not eating right away, I like to wrap the sandwich in parchment paper before slicing. Otherwise, slice into smaller, individual sandwiches, then enjoy!