Preheat oven to 400°. Line a baking sheet with parchment paper or lightly spray with nonstick cooking spray.
Cut the French bread in half end-to-end like youre going to make a giant sandwich. Cut those halves in half again and arrange the pieces of bread on the prepared baking sheet. Drizzle the extra virgin olive oil evenly over the cut surfaces of the bread and place the pan in the oven, toasting until the edges of the bread turn golden brown. Remove the pan from the oven and spread the Alfredo sauce over the toasted bread. Divide and scatter the spinach, then mozzarella cheese over the Alfredo sauce. If using the prosciutto, arrange that over the top of the mozzarella cheese. Bake for 10-15 minutes, or until the cheese is fully melted and bubbly. If you like the cheese to have little toasted brown areas, you can leave the pizzas in for another 5 minutes or until it is done to your liking.