In a large saucepan, heat 2 tablespoons of olive oil over medium heat for about 2 minutes. Once the oil shimmers, add one chopped large onion and a thinly sliced small fennel bulb. Sauté until softened and translucent, roughly 5 minutes, stirring occasionally to prevent burning.

Pour in 4 cups of reduced-sodium chicken broth or vegetable broth. Stir in one can of cannellini beans, one can of diced tomatoes, 1 teaspoon of dried thyme, and 1/4 teaspoon of pepper. Toss in one bay leaf for added depth. Bring this mixture to a boil for about 5 to 7 minutes.

Once boiling, reduce the heat to low, cover the saucepan, and let the soup simmer gently for about 30 minutes, allowing flavors to meld. The fennel will tenderize.

Carefully remove the bay leaf and stir in 3 cups of shredded fresh spinach, allowing it to wilt into the soup. Cook for an additional 3 to 4 minutes over low heat until the spinach is tender yet bright.

Ladle generous portions into bowls, and consider garnishing with fresh herbs or a sprinkle of your favorite cheese. Serve warm.