Pick the leaves off the stems of the watercress and discard the stems.
Remove the fava beans from the long pods, place them in a saucepan, cover with water, and simmer 3 minutes. Drain and transfer the beans to a bowl of ice water.
Place the raisins in a dish of warm water and set aside to soak for 15 minutes.
Peel the skins off the fava beans.
Drain the raisins and pat them dry.
Arrange the watercress leaves on each of the 4 plates.
Scatter the fava beans and raisins over the watercress, drizzle with the olive oil, then top with shavings of pecorino.
Season with salt and pepper and serve.