for the sauce: 0.75 cups smooth peanut butter 3 tablespoons soy sauce 2 tablespoons rice vinegar or white wine vinegar 1 tablespoon lime juice 1 small garlic clove -minced cayenne pepper to taste half cup hot water dozen ounces pasta -i.e. rotelle, -penne, farfelle 2 carrots -cut into thin -slices on a -diagonal 1.5 cup broccoli florets half pound snow peas -trimmed and cut -crosswise into -1-inch pieces 4 scallions -thinly sliced