Heat vegetable broth in medium saucepan over medium heat.
In a large stock pot, heat olive oil over medium-high heat. Add onions and saute for approximately 3 minutes. Add garlic, salt, and red pepper flake. Add diced prosciutto and continue to saute for 2-3 minutes.
Add arborio rice to pan and stir to coat with onion mixture. Add in white wine; stir until most liquid is absorbed.
Add 1/2 cup of the warmed broth to rice mixture, stirring to incorporate. Continue to add broth at 1/2 cup increments, stirring between each addition until the liquid is mostly absorbed. You will want to make sure you are stirring the risotto almost constantly to ensure it doesn't burn and the liquid is absorbed properly. Continue until a total of 4 cups of broth have been added to the rice. Test the rice at this point - you are looking for it to be slightly al dente and creamy. It will likely need more broth and cooking time. Continue adding broth until the rice reaches the al dente point (test between each addition as the "magic point" will come quickly!). Add corn and cook for 1 minute.
Remove risotto from heat; stir in the shredded parmesan cheese and butter until melted completely.
Serve immediately; garnish with chopped parsley and additional parmesan cheese if desired.
Notes
If you have a 32-ounce broth container and don't want to open another, you can substitute water for the remaining 2 cups of broth.