Prepare a medium-hot fire in a grill or preheat a skillet over medium-high heat. Place the fig halves cut side down on the grill or in the skillet and grill for a few minutes, until the cut sides start to caramelize. Meanwhile, grill or toast the bread. Spread each slice of bread with the crescenza. Place 2 fig halves on each slice of bread, Lay a slice of prosciutto over the figs, scatter a few arugula leaves on top and serve.