Heat the olive oil in a large heavy pot or Dutch oven over medium-high heat. Add the chorizo and cook, stirring often, until it has rendered its fat and is beginning to brown, 3 to 4 minutes. Add the onions, celery, and carrots and cook, stirring often, until softened, about 3 minutes. Add the salt and pepper and stir well.
Add the kale, garlic, bouquet garni, chicken stock, and red pepper flakes. Bring to a boil over high heat, stirring occasionally. Reduce the heat to medium-low. Simmer, stirring occasionally, until the kale is tender, about 30 minutes.
Add the clams and cook until they open, about 10 minutes. Discard any unopened clams.
Stir in the cilantro. Serve hot.
Yield: 8 to 12 servings