In nonstick Dutch oven, bring broth to a boil. Add pasta and chicken. Reduce heat; cover and simmer 9 to 11 minutes or until pasta is of desired doneness.
In small bowl or jar with tight-fitting lid, combine 1 cup of the milk and flour. Beat with wire whisk or shake until well blended.
Add flour mixture, remaining 3 cups milk, peas, pimientos, basil and pepper to broth mixture; cook and stir over medium heat until soup is bubbly and thickened and chicken is no longer pink. If desired, add salt to taste.