1. Cut focaccia in half horizontally. Cut teleme or jack cheese into 1/2-inch-thick slices. Lay slices (or spread crescenza) on bottom half of focaccia and cover evenly with prosciutto. Place both focaccia pieces (the top, cut side up) on a 14- by 17-inch baking sheet.
2. Bake in a 450° oven until cheese begins to melt and bread is crusty, about 8 minutes (about 6 minutes in a convection oven).
3. Arrange arugula over prosciutto. Using a wide spatula, set focaccia top, cut side down, on arugula. Slide focaccia sandwich onto a board and cut into 6 pieces.
Nutritional analysis per piece.