To prepare soup, heat olive oil in a large Dutch oven over medium-high heat. Add onion, carrot, and celery; sauté 6 minutes or until onion is tender. Add minced garlic; cook 1 minute. Stir in potato and sage. Stir in broth; bring to a boil. Cover, reduce heat, and simmer 10 minutes. Stir in chard; simmer an additional 10 minutes or until potatoes are tender. Add 1/2 teaspoon salt, 1/4 teaspoon black pepper, and pinto beans. Simmer 5 minutes or until hot. Remove from heat; keep warm.
To prepare herb pesto, combine basil and remaining ingredients except bread in a food processor. Process until smooth, scraping the sides with a spatula. Spread 1 1/2 teaspoons pesto over each bread slice. Ladle 1 cup soup into each of 8 bowls. Tuck 1 pesto-topped bread slice into each serving.