Bring the water to a boil in a large saucepan; gradually stir in grits. Reduce heat, and simmer 30 minutes or until thick, stirring frequently. Remove from heat. Stir in 1/4 cup cheese and 1/2 teaspoon salt. Spoon grits mixture into an 11 x 7-inch baking dish coated with cooking spray.
Preheat oven to 350°.
Melt butter in a large nonstick skillet over medium-high heat. Add onion and garlic; sauté 3 minutes or until tender. Add remaining 1/2 teaspoon salt, mushrooms, herbes de Provence, and pepper; cook 6 minutes or until mushrooms are tender, stirring frequently. Stir in prosciutto and wine; cook 5 minutes or until liquid almost evaporates. Remove from heat; cool slightly. Stir in eggs and egg whites. Spread mushroom mixture over grits mixture; sprinkle with remaining 1/2 cup cheese. Bake at 350° for 30 minutes or until cheese melts and grits are thoroughly heated, and let stand 5 minutes before serving. Sprinkle with parsley.