How to Make It
In a large, deep skillet, heat the olive oil until shimmering. Add the red onion, prosciutto and a pinch of salt and cook over moderate heat, stirring occasionally, until the onion is softened, 5 to 7 minutes.
Stir in the peas and water and bring to a boil. Simmer over moderately low heat, stirring occasionally, until the peas are tender and almost all of the water has evaporated, 15 to 20 minutes. Stir in the pepper and 1/4 cup of cheese and season with salt. Transfer the peas to a large bowl and serve, passing more cheese at the table.