How to Make It
In a large pot, heat the oil. Add the shallot, parsley, garlic and crushed red pepper. Cook over moderate heat, stirring, until fragrant, about 2 minutes. Add the escarole, kale and chard and cook, stirring, until the greens start to wilt, about 2 minutes. Add the stock and bring to a boil. Simmer until the greens are tender, about 20 minutes.
Meanwhile, spread the butter on both sides of the bread slices. Heat a large nonstick skillet. Add the baguette slices and toast over moderate heat until golden, 2 to 3 minutes per side.
Stir the vinegar into the soup and season with sea salt and white pepper. Ladle the soup into bowls, top with the toasts and garnish with the grated cheese.