In a large saucepan, cook pasta according to package directions, adding the edamame during the last 5 minutes of cooking. Meanwhile, using a vegetable peeler or metal cheese slicer, cut carrots and squash into very thin lengthwise strips.
In a large skillet, saute onion in 1 tablespoon butter until tender. Add the vegetable strips and garlic; saute 2-3 minutes longer or until crisp-tender. Stir in the cream, pesto, salt and remaining butter. Bring to a gentle boil; cook for 2-4 minutes or until sauce is slightly thickened and vegetables are tender.
Drain pasta and edamame; toss with vegetable mixture. Sprinkle with walnuts.