In a small saucepan, pour in about 1 inch of oil and heat it over medium heat. Add the sliced shallots and cook them, stirring frequently, until they turn golden brown and crispy, which should take about 8 to 10 minutes. Once done, use a slotted spoon to transfer the shallots to a plate lined with paper towels and sprinkle them with a pinch of salt. Set them aside.

In a food processor or blender, combine the avocado, mayonnaise, garlic, lemon juice, Dijon mustard, salt, and black pepper. Blend the mixture until it becomes smooth and creamy. Place it in the refrigerator until you're ready to use it.

Pat the skirt steak dry and season it generously with kosher salt and black pepper. Heat a drizzle of oil in a cast-iron skillet over medium-high heat. When the skillet is very hot, add the steak and cook it until it is deeply browned and reaches your desired level of doneness, which should take about 2 to 3 minutes per side for medium-rare. Once cooked, transfer the steak to a cutting board and let it rest for 5 to 10 minutes before slicing it thinly against the grain. Alternatively, you can grill the steak over high heat for the same amount of time.

While the steak is resting, toast the ciabatta rolls until they are golden brown. In the last 1 to 2 minutes of toasting, place provolone cheese on the bottom halves of the rolls and continue to toast until the cheese melts.

Spread the avocado garlic aioli on both cut sides of the toasted ciabatta. On the bottom halves, layer the arugula, followed by the sliced steak, crispy shallots, and sliced avocado. Top with the remaining halves of the bread.

Slice the sandwiches in half and serve them immediately, with extra avocado garlic aioli on the side if desired.