Preheat oven to 350°. Melt butter in a 10-inch skillet over medium heat. Add onion and mushrooms. Sauté until limp and translucent. Add rice. Sauté briefly. Stir in ham, chicken stock, saffron, if desired, white wine and parsley. Stir to blend. Bring to a full boil and pour into a 1-quart casserole. Cover and bake 30 minutes. While casserole is baking, thaw peas. Remove casserole from oven. Stir in peas and salt and pepper. Sprinkle Parmesan cheese evenly over top. Bake, uncovered, 15 minutes more. Makes 2 servings. This recipe can be doubled or tripled for more servings. I often make it and omit the saffron and white wine. Try adding a mixture of herbs such as oregano, garlic, basil and thyme. This dish is both delicious and quick!