Heat oil in a large pot or Dutch oven over medium-low.
Add fennel, onion, garlic, salt, black pepper, and red pepper flakes, and cook until softened, about 5 minutes.
Stir in oregano and cook 30 seconds.
Stir in tomatoes with their juices and broth, bring soup to a boil then reduce to a simmer and cook for 10 minutes.
Stir in kale, simmer 10 minutes.
Stir in chickpeas and vinegar and simmer 5 minutes. Season soup with additional salt, pepper flakes, and vinegar to taste.
Drizzle servings with olive oil and top with chopped fennel fronds.
Notes
* Don’t have oregano? Rosemary or thyme will also work.** Can't find Tuscan kale? It's often labeled Dinosaur or Lacinato kale as well. However, regular curly-leaf kale will work just fine!Serve over rice for a heartier stew-like dish.Store leftovers in an airtight container in the refrigerator for up to 4 days. Reheat leftovers in a saucepan over medium-low heat or individual servings in the microwave for 2 minutes on high. Add additional water to thin as needed.