Slice open the ciabatta roll in half horizontally and drizzle both sides with olive oil.
Spread basil pesto on the bottom half of the roll.
Layer prosciutto evenly over the pesto.
Stack tomato slices over the prosciutto, followed by arugula and slices of mozzarella or burrata.
Drizzle balsamic glaze on top of the cheese and sprinkle with pepper flakes or black pepper.
Top the sandwich with the upper half of the ciabatta roll and press down gently.
Add a trivet to the pressure cooker with a bit of water. Place sandwich on trivet and lock lid.
Cook on low pressure for 5 minutes. Let naturally release before serving.
Notes
You can substitute sourdough for ciabatta and burrata instead of mozzarella. Do not use balsamic vinegar in place of glaze—it will make the sandwich soggy.