Melt 2 Tbs of the butter in a heavy saucepan over moderate heat and cook the chopped onions for 7 or 8 minutes, stirring frequently, until soft but not brown.
Add the peas and chicken stock and cook 15 to 20 minutes, covered.
When the peas are tender, add the prosciutto and cook uncovered for 2 minutes, stirring, until the liquid is absorbed.
Season to taste with salt and pepper.
Notes
Excellant side dish that is always popularNote:You can use either fresh peas or frozen peas that have been thawed.