Preheat oven to 350°. Beat ricotta and cream cheese until smooth. Add eggs, butter, salt and pepper; beat until blended. In another bowl, whisk flour with baking powder; add to egg mixture. Stir in Gruyere and chives. Pour into a greased 13x9-in. baking dish. Sprinkle with Parmesan., Bake, uncovered, until a knife inserted in center comes out clean, 25-30 minutes. Let stand 10 minutes before cutting.