Dissolve salt in cold water in a large container. Add the chickpeas and soak at room temperature for at least 8 hours or up to 24 hours. Drain and rinse them well before using.

Heat oil in a Dutch oven over medium heat until it begins to shimmer. Add the fennel, onion, and salt, and cook until the vegetables are softened and translucent, 7 to 10 minutes.

Stir in the garlic, oregano, and pepper flakes and cook until fragrant, about 30 seconds.

Stir in the water, broth, drained chickpeas, Parmesan rind, bay leaves, and orange zest and bring the liquid to a boil. Reduce the heat to a gentle simmer and cook until the chickpeas are tender but not falling apart, 1 1/4 to 1 3/4 hours.

Stir in the escarole and tomato and continue to cook until the escarole is completely wilted, 5 to 10 minutes.

Remove the pot from the heat. Discard the bay leaves and Parmesan rind, making sure to scrape any melted cheese from the rind back into the stew. Season with salt and pepper to taste. Serve hot, topped with a dusting of grated Parmesan and a light drizzle of oil.