How to Make It
Add the grapes, balsamic vinegar, shallots, sugar, and water to a small saucepan and cook over medium to low heat until the grapes cook down slightly and release their juices, about 7 minutes. Season with salt and pepper and set aside.
Toast the baguette slices until they're crispy on the edges and lightly golden brown. Drizzle one surface of each piece with olive oil and season with salt.
Transfer the crostini to a serving plate. Place one or two thin slices of the ricotta salata and fold half a prosciutto slice onto each toast. Spoon a few grapes into the layers of the prosciutto, drizzle with the grape syrup and olive oil just before serving. Season the crostini with sea salt and freshly ground black pepper.