Step 1

In a large pot over medium heat, heat oil.

Step 2

Add the onion, and celery, about 5 minutes.

Step 3

Add garlic, thyme, and red pepper flakes (if using) and cook until fragrant, 1 minute more.

Step 4

Add the escarole and stir until wilted completely.

Step 5

Season well with salt and pepper.

Step 6

Add the broth, beans, parmesan rind and bay leaves and bring to a boil.

Step 7

Reduce heat to a simmer, and stir occasionally, mashing some beans (about 1/3 of them) in the pot to thicken soup.

Step 8

Let simmer 15 minutes, then stir in lemon juice.

Step 9

Garnish with grated Parmesan cheese before serving.