Mushroom Ragout With Prosciutto au Sherry

9 oz. baby bella mushrooms,
1 oz. prosciutto ham,
1 & 1/4 oz. shallots or onions,
4 garlic cloves,
2 T. butter,
1 T. flour,
1/2 c. chicken broth,
1/ 4 c. dry sherry,
1 stem fresh rosemary,
1/4 c. heavy cream,
1/2 tsp. salt,
1/4 tsp. black pepper.