Sprinkle flour over vegetables and stir well with wire whisk to incorporate. Cook about 2 minutes. Stirring constantly, slowly add broth and wine (make sure to scrape bottom of pan as flour tends to stick). Stir in corn, potatoes, half-and-half, thyme, salt, pepper if desired, bay leaf and nutmeg. Heat soup to a gentle simmer. Cook 15 minutes, stirring occasionally, until potatoes are tender. (Corn can be naturally salty depending on the season, so make sure to taste before adding extra salt.) Remove bay leaf.