Warm the olive oil in a 4-quart Dutch oven or soup pot over medium heat.

Add the onion, carrots, and celery. Cook for 5 to 7 minutes, stirring now and then, until the onion turns translucent and the vegetables begin to soften.

Stir in the garlic, crushed red pepper flakes, and some black pepper. Cook for about 1 minute, stirring often to prevent the garlic from browning.

Pour in the vegetable stock and add the drained, rinsed beans. Bring the soup to a boil, then lower the heat and simmer for 15 to 20 minutes, or until the vegetables are soft.

Add the chopped escarole a few handfuls at a time, pushing it gently into the hot soup as it wilts. Simmer for another 3 to 5 minutes, until the escarole is tender.

Taste the soup and adjust the salt and black pepper as needed. Ladle it into bowls, drizzle each serving with a little olive oil, and serve with crusty bread.

Let any leftover soup cool, then place it in airtight containers. Refrigerate for up to 4 days or freeze for up to 1 month. Reheat gently before serving.