1. Preheat oven to 400°.
2. To prepare soufflés, coat each of 4 (1-cup) soufflé dishes evenly with 1/2 teaspoon butter. Sprinkle each soufflé dish with 2 teaspoons Parmigiano-Reggiano cheese, tilting to coat sides and bottom.
3. Combine flour and the next 3 ingredients (through black pepper) in a small saucepan over medium heat. Gradually add milk and white wine, stirring with a whisk until smooth. Cook for 4 minutes or until mixture is thick and bubbly, stirring constantly. Remove from heat. Add salt and Gruyère cheese; stir until cheese melts. Spoon the mixture into a large bowl, and let stand for 5 minutes. Stir in egg yolks.
4. Place egg whites in a large bowl; beat with a mixer at high speed until medium peaks form (do not overbeat). Gently stir one quarter of egg whites into yolk mixture; gently fold in the remaining egg whites. Gently spoon mixture into prepared dishes. Place dishes on a baking sheet, and place in 400° oven. Immediately reduce oven temperature to 375°. Bake soufflés at 375° for 17 minutes or until puffy and golden.
5. To prepare salad, combine olive oil, vinegar, salt, and black pepper in a large bowl, stirring well with a whisk. Add arugula and herbs; toss to coat. Serve with soufflés.