Preheat oven to 450°. Combine first 3 ingredients in a food processor. Add butter, and pulse until mixture forms a coarse crumble. Add prosciutto, cheese, and rosemary; pulse to combine. Add cream, pulsing just until combined. (Dough will be crumbly.)
Press or pat dough into an 8-inch round, and cut into 8 wedges. Place wedges 2 inches apart on a lightly greased baking sheet, and brush tops with egg.
Bake 12 to 15 minutes or until golden brown.