Lightly brush one side of each bread slice with olive oil. Place the bread (oil side down) on a preheated indoor grill or panini maker, and layer with arugula, pancetta and a good drizzle of the vodka mayo. Place the other slice of bread on top, oil side up. Repeat as many times as you can to fit the sandwiches on the grill. Place another cast iron on top of the sandwiches (or lower the top of the panini maker) and grill for 3 minutes on each side. Or use a panini press!