Position a rack in the upper third of the oven, place a baking sheet on the rack and preheat to 450 degrees F. Lightly grease a 9-inch round or 8-inch square baking dish with olive oil.
Pulse the gouda in a food processor until finely chopped. Add the spinach, whole eggs and egg whites, ricotta, flour and nutmeg and process until well combined, about 30 seconds. Add the scallions and pulse to mix.
Pour the mixture into the prepared dish and sprinkle with the parmesan and paprika. Place the quiche on the preheated baking sheet and bake until the center is just set, 25 to 30 minutes.
Drizzle the endive and walnuts lightly with olive oil and toss. Serve the quiche hot or at room temperature with the endive.
Per serving: Calories 389; Fat 24 g (Saturated 12 g); Cholesterol 175 mg; Sodium 523 mg; Carbohydrate 16 g; Fiber 3 g; Protein 28g