Preheat oven to 350°. Spread pesto on 1 side of each bread slice. Cut each bread slice into 1/2- to 1-inch cubes. Place bread cubes in a single layer on a lightly greased aluminum foil-lined jelly-roll pan.
Bake at 350° for 16 to 20 minutes or until golden, turning once after 10 minutes. Remove from oven, and let cool.
Melt butter with oil in a large Dutch oven over medium-high heat. Add garlic and shallot, and cook, stirring constantly, 2 minutes or until vegetables are tender. Add tomato paste, and cook, stirring constantly, 1 minute. Stir in bell peppers and chicken broth; bring to a boil. Reduce heat to medium, and simmer, stirring occasionally, 5 minutes. Remove from heat; let cool 10 minutes.
Process red pepper mixture, in batches, in a blender or food processor 8 to 10 seconds until smooth, stopping to scrape down sides. Return red pepper mixture to Dutch oven; stir in half-and-half and parsley, and cook over medium heat 5 minutes or until thoroughly heated. Season with salt and pepper to taste.
Ladle soup into 6 bowls; top with croutons. Garnish, if desired.