Spinach and Ricotta Stuffed Shells

In April I finally broiled something correctly, so I took a picture and posted it on Facebook.  The dish happened to be Real Simple's Spinach and Ricotta Stuffed Shells recipe, and I guess it looked good because some of my friend's wanted the recipe.  I add prosciutto to mine because I am such the meatatarian, but this is supposed to be a vegetarian dish.  Of course this means I always have way too much stuffing leftover, but I just make a bigger dish and have more cheesy-prosciutto goodness.

My only caution to anyone making this is to be careful with the broiler.  Usually I am so scared to burn things I don't get the nice browning effect, but this time I just kept watching through the oven door.  Plus, this oven can broil on different temperatures (I don't think all ovens do this, but I'm not sure), so I had it on a lower temperature.
 

Spinach and Ricotta Stuffed Shells
adapted from Real Simple 

20 jumbo pasta shells 
1 24-ounce jar marinara sauce
2 15-ounce containers ricotta
2 cups baby spinach, chopped
1/2 cup grated Parmesan
Kosher salt
Black pepper
1 cup grated mozzarella
4 ounces prosciutto (optional)

• Set an oven rack to the highest position and heat oven to 400 degrees.
• Cook the pasta according to the package, drain and run under cold water.
• Spread the marinara sauce in the bottom of a large broilerproof baking dish.
• In a bowl, combine the ricotta, spinach, Parmesan, 1/2 teaspoon salt, and 1/4 teaspoon pepper (and prosciutto if you're going my route).  Spoon the mixture into the shells and place them on top of the sauce.  Sprinkle with the mozzarella and bake until the shells are heated through, 10 to 12 minutes.
• Increase the heat to broil.  Broil the shells until the cheese begins to brown, 2 to 5 minutes.