Heat a large heavy bottomed pot or Dutch oven over medium heat.
Add the olive oil, then add the sausage. Break it up with a wooden spoon and cook until browned, about 6-8 minutes.
Add the garlic, fennel seed, oregano, and red chili flakes along with a small pinch of salt. Cook, stirring often, until the garlic softens but does not take on any color, about 2 minutes.
Pour in the chicken stock and bring up to a simmer, then add the beans and stir to coat.
Add the escarole, then cover and let it cook down. If your pot can’t fit it all at once, add a few handfuls at a time and let it wilt down before adding the rest. Give it a good stir to combine.
Cover the pot and simmer on low heat for about 20 minutes, stirring occasionally.
Taste and adjust seasoning with additional salt or chili flakes if needed.
Spoon into bowls and serve hot with plenty of crusty bread and grated Pecorino Romano on the side.
