1 To make walnut pesto, place basil, parsley, sage, walnuts, cheese and garlic in food processor and process until finely ground. 2 Add juice, then with motor running, slowly add oil and process until mixture is thick and emulsified. Season with salt to taste. Set aside.3 Toss flageolets, black beans and haricots vert together in large bowl. 4 Add pesto and toss to combine and coat evenly. Season to taste with salt and pepper.5 Spoon about 3 tablespoons bean mixture into each of 4 lettuce leaves. Top each with a walnut half and, if desired, garnish with an herb sprig.