Sausage-and-Kale Soup

INGREDIENTS

• 1 tablespoon olive oil
• 1 onion, diced
• 2 garlic cloves, minced
• 1/4 teaspoon crushed red-pepper flakes
• 5 waxy potatoes (1 1/2 pounds), peeled and cut into 1/2-inch chunks
• 3 cans (14 1/2 ounces each) reduced-sodium chicken broth
• 1 bunch kale (12 ounces), stemmed and shredded
• 12 ounces smoked chicken sausage, cut into 1/2-inch half moons