In a large stockpot, heat olive oil. Add onions and saute until softened. Stir in garlic and cook until just fragrant.

Add stock and potatoes. Stir occasionally over medium heat until potatoes are softened, about 15-20 minutes.

Add cooked meatballs, collard greens, tomato paste, salt, pepper, oregano and cayenne. Allow flavors to meld and greens to wilt, about 15 minutes. Season to taste. To serve, ladle into bowls and sprinkle with goat cheese crumbles.