Special equipment: a campfire; a large cast-iron pot
Heat the olive oil in a large cast-iron pot over a medium-high open flame. Add the bacon and cook, stirring often, until crispy, about 10 minutes. Add the garlic, celery and onion and cook, stirring occasionally, until softened, about 10 minutes.
Stir in the tomatoes and bring the mixture to a boil. Add the cannellini beans and chicken broth, bring to a simmer, and cook, covered, stirring occasionally, for 20 minutes. Stir in the parsley and season with salt and pepper. Ladle the beans into bowls, garnish with Pecorino and serve.