Dainty shredded-wheat "nests" are filled with a colorful salad of tomatoes, mozzarella, and green beans. Handle these nests very carefully, since they're just as fragile as real birds' nests.
Preheat oven to 350 degrees. Gently pull apart shredded wheat into strands and small pieces; transfer to a large bowl. Add flour and Parmesan cheese; season with salt and pepper. Toss. Add melted butter, and toss.
Lightly coat 6 cups of a 12-cup standard muffin tin with cooking spray. Press about 1/4 cup shredded-wheat mixture into each of the 6 cups, pressing up around sides to form a nest. Bake until nests begin to turn golden brown, 8 to 9 minutes. Let cool completely in tin. To unmold, gently twist nests in cups, and then carefully pull up. Nests can be stored in an airtight container at room temperature up to 2 days before you fill them with vegetables.
Prepare an ice-water bath; set aside. Bring a medium saucepan of water to a boil; add salt. Cook beans until crisp-tender, 2 to 3 minutes. Transfer to the ice-water bath to stop the cooking. Drain, and pat dry with paper towels. Cut beans into 1-inch pieces. Transfer to a large bowl. Add tomatoes and mozzarella; toss. The vegetable mixture can be refrigerated in an airtight container up to 1 day.
Just before serving, whisk together vinegar and oil in a small bowl; season with salt and pepper. Toss vegetable mixture with the vinaigrette. Transfer nests to serving plates. Fill with salad, dividing evenly.